Broken Authentication Testing Tool For Rest Apis — Complete Documentation & Simulation

Overview & System Context

Broken Authentication Testing Tool For Rest Apis: Comprehensive Web-Sourced Technical Investigation Exhaustive Research Dossier · Pure Web-Scraped Content: ~9076 Words · Real Software Screenshots: 3 1. Executive Overview & Technical Background Web Authentication (WebAuthn) is a web standard published by the World Wide Web Consortium (W3C). It defines an API that websites use to authenticate with WebAuthn credentials (commonly known as passkeys) and outlines what WebAuthn authenticators should do. It solves many of the issues of traditional password-based authentication by verifying the user's identity with digital signatures. Although WebAuthn is often touted as a complete replacement for passwords, most websites that implement it continue to use passwords in some capacity. To use WebAuthn, users require a compatible authenticator.

The standard does not specify how to store the keys required for signing, so a variety of authenticator types can be used. The most common authenticator type is a platform authenticator, which is built into the operating system of the device. Common platform authenticators include Android, Apple Keychain and Windows Hello. These make use of hardware security features (such as TEE and TPM), and often sync credentials between devices for ease-of-use. Another common authenticator type is a roaming authenticator, where a separate hardware device authenticates the user by connecting over USB, Bluetooth Low Energy, or near-field communications (NFC). Most smartphones can be used as roaming authenticators, and dedicated physical security keys are also used. WebAuthn is effectively backward compatible with FIDO Universal 2nd Factor (U2F) as they both use the CTAP protocol. Password managers can also be used as an authenticator, often with cloud sync. Where credentials sync is not viable or possible, WebAuthn Hybrid Transport can be used to access credentials stored on another authenticator such as a smartphone. Like legacy U2F, WebAuthn is resistant to some phishing attacks as the authenticator only offers credentials that were registered on the same website. However, unlike U2F, WebAuthn can be implemented in a passwordless manner. Moreover, a roaming hardware authenticator resists malware, since the keys are stored on a separate device, which prevents the malware from accessing them directly. The WebAuthn Level 1 and 2 standards were published as W3C Recommendations on 4 March 2019 and 8 April 2021 respectively. A Level 3 specification progressed through several Candidate Recommendation Snapshots during 2026, and in July 2026 the W3C proposed advancing it to full Recommendation status.

Passkey is the de facto non-technical term for a saved sign-in credential, a piece of cryptographic information that is capable of being used to authenticate a user using the WebAuthn standard. Most user interfaces that support using WebAuthn refer to it as supporting passkeys. Due to the open-ended nature of the WebAuthn specification, a passkey can be stored on software or hardware that is capable of authenticating a user. This includes technology like Windows Hello which works by using facial recognition to authenticate users, Bitwarden which authenticates users through a browser extension or YubiKeys that allow a user to authenticate using a physical hardware token. The cryptographic keys stored by the software are only available to use for the browser once the software or hardware is authenticated the user. When Apple first prominently introduced passkeys to the public in 2022, they emphasized integrations with their own products. This, combined with the lack of clear communication from other companies, led to speculation that passkeys were proprietary to Apple. As browsers and websites began to implement WebAuthn, the inconsistent feature-sets have often resulted in a variety of understandings of what exactly counted as a passkey.

The website is a conforming WebAuthn Relying Party The browser is a conforming WebAuthn Client The authenticator is a FIDO2 authenticator, that is, it is assumed compatible with the WebAuthn Client WebAuthn specifies how a claimant demonstrates possession and control of a FIDO2 authenticator to a verifier called the WebAuthn Relying Party. The authentication process is mediated by an entity called the WebAuthn Client, which is little more than a conforming web browser.

Authenticator is a multi-factor cryptographic authenticator that uses public-key cryptography to sign an authentication assertion targeted at the WebAuthn Relying Party. Assuming the authenticator uses either a facial recognition, fingerprint or PIN for user verification, the authenticator itself is something you have while the facial recognition and fingerprint (biometric) are something you are and the PIN is something you know. To initiate the WebAuthn authentication flow, the WebAuthn Relying Party indicates its intentions to the WebAuthn Client (i.e., the browser) via JavaScript. The WebAuthn Client communicates with the authenticator using a JavaScript API implemented in the browser. A roaming authenticator conforms to the FIDO Client to Authenticator Protocol (CTAP), and connected over USB, Bluetooth Low Energy, or near-field communications (NFC). WebAuthn does not strictly require a roaming hardware authenticator. Alternatively, a software authenticator (e.g., implemented on a smartphone) or a platform authenticator (i.e., an authenticator implemented directly on the WebAuthn Client Device) may be used. Relevant examples of platform authenticators include Windows Hello and the Android operating system. WebAuthn Hybrid Transport allows the WebAuthn Client to access credentials stored on another authenticator such as a smartphone, useful in certain situations where credential sync is not viable. There is a lingering misunderstanding among users that biometric data is transmitted over the network in the same manner as passwords, which is not the case.

Figure 1: Broken User Authentication in Modern APIs: A Technical Deep Dive | by ... The WebAuthn Level 1 standard was published as a W3C Recommendation by the Web Authentication Working Group on 4 March 2019. WebAuthn is supported by Google Chrome, Mozilla Firefox, Microsoft Edge, Apple Safari and Opera. The desktop version of Google Chrome has supported WebAuthn since version 67. Firefox, which had not fully supported the previous FIDO U2F standard, included and enabled WebAuthn in Firefox version 60, released on 9 May 2018. An early Windows Insider release of Microsoft Edge (Build 17682) implemented a version of WebAuthn that works with both Windows Hello as well as external security keys. Existing FIDO U2F security keys are largely compatible with the WebAuthn standard, though WebAuthn added the ability to reference a unique per-account "user handle" identifier, which older authenticators are unable to store. One of the first FIDO2-compatible authenticators was the second-generation Security Key by Yubico, announced on 10 April 2018. The first FIDO2-compatible authenticators with a display was Trezor Model T by SatoshiLabs, announced on 6 November 2019. Trezor Model T was also the first authenticator that allowed users to select which FIDO2 resident credential should be used directly on a device. The first Security Level 2 certified FIDO2 key, called "Goldengate" was announced one year later by eWBM on 8 April 2019. Dropbox announced support for WebAuthn logins (as a 2nd factor) on 8 May 2018. Apple announced that Face ID or Touch ID could be used as a WebAuthn platform authenticator with Safari on 24 June 2020. Several password managers such as Bitwarden and Dashlane support WebAuthn.

Through the mandated use of COSE (RFC 8152) WebAuthn also supports RSA with PKCS1v1.5 padding. This particular scheme of padding has been known to be vulnerable to specific attacks for at least twenty years, and it has been successfully attacked in other protocols and implementations of the RSA cryptosystem in the past. It is difficult to exploit under given conditions in the context of WebAuthn, but since there are more secure cryptographic primitives and padding schemes, it is still a bad choice and cryptographers no longer consider it best practice. The FIDO Alliance standardized on the asymmetric cryptographic scheme ECDAA. This is a version of direct anonymous attestation based on elliptic curves and in the case of WebAuthn is used to verify the integrity of authenticators, while also preserving the privacy of users, as it does not allow for global correlation of handles. However, ECDAA does not incorporate some of the lessons that were learned in the last decades of research in the area of elliptic curve cryptography, as the chosen curve has some security deficits inherent to this type of curve, which reduces the security guarantees quite substantially. Furthermore, the ECDAA standard involves random, non-deterministic signatures, which already has been a problem in the past. Paragon Initiative Enterprises also criticized how the standard was initially developed, as the proposal was not made public in advance and experienced cryptographers were not asked for suggestions and feedback. Hence the standard was not subject to broad cryptographic research from the academic world. Despite these shortcomings, Paragon Initiative Enterprises still encourage users to continue to use WebAuthn but have come up with some recommendations for potential implementers and developers of the standard that they hope can be implemented before the standard is finalized. Avoiding such mistakes as early as possible would protect the industry from any challenges that are introduced by broken standards and the need for backwards compatibility. ECDAA was only designed to use in combination with device attestation. This particular feature of WebAuthn is not necessarily required for authentication to work. Current implementations allow the user to decide whether an attestation statement is sent during the registration ceremony. Independently, relying parties can choose to require attestation or not. ECDAA was removed from WebAuthn Level 2 as it was not implemented by browsers nor relying parties.

Transport Layer Security (TLS) is a cryptographic protocol designed to provide secured communications over a computer network, such as the Internet. The protocol is widely used in applications such as email, instant messaging, and voice over IP, but its use in securing HTTPS remains the most publicly visible. The TLS protocol aims primarily to provide security, including privacy (confidentiality), integrity, and authenticity through the use of cryptography, such as the use of certificates, between two or more communicating computer applications. It runs in the presentation layer and is itself composed of two layers: the TLS record and the TLS handshake protocols. The closely-related Datagram Transport Layer Security (DTLS) is a communications protocol that provides security to datagram-based applications. In technical writing, references to "(D)TLS" are often seen when it applies to both versions. TLS is a proposed Internet Engineering Task Force (IETF) standard, first defined in 1999, and the current version is TLS 1.3, defined in August 2018. TLS builds on the now-deprecated SSL (Secure Sockets Layer) specifications (1994, 1995, 1996) developed by Netscape Communications for adding the HTTPS protocol to their Netscape Navigator web browser.

The handshake begins when a client connects to a TLS-enabled server requesting a secure connection and the client presents a list of supported cipher suites (ciphers and hash functions). From this list, the server picks a cipher and hash function that it also supports and notifies the client of the decision. The server usually then provides identification in the form of a digital certificate. The certificate contains the server name, the trusted certificate authority (CA) that vouches for the authenticity of the certificate, and the server's public encryption key. The client confirms the validity of the certificate before proceeding. To generate the session keys used for the secure connection, the client either: encrypts a random number (PreMasterSecret) with the server's public key and sends the result to the server (which only the server should be able to decrypt with its private key); both parties then use the random number to generate a unique session key for subsequent encryption and decryption of data during the session, or uses Diffie–Hellman key exchange (or its variant elliptic-curve DH) to securely generate a random and unique session key for encryption and decryption that has the additional property of forward secrecy: if the server's private key is disclosed in the future, it cannot be used to decrypt the current session, even if the session is intercepted and recorded by a third party. This concludes the handshake and begins the secured connection, which is encrypted and decrypted with the session key until the connection closes. If any one of the above steps fails, then the TLS handshake fails and the connection is not created. Older versions of TLS and SSL allowed for establishing sessions via a PreMasterSecret using the server's public and private key. These algorithms were eliminated in TLS1.3 when it mandated forward secrecy. TLS and SSL do not fit neatly into any single layer of the OSI model or the TCP/IP model. TLS runs "on top of some reliable transport protocol (e.g., TCP)", which would imply that it is above the transport layer. It serves encryption to higher layers, which is normally the function of the presentation layer. However, applications generally use TLS as if it were a transport layer, even though applications using TLS must actively control initiating TLS handshakes and handling of exchanged authentication certificates. When secured by TLS, connections between a client (e.g., a web browser) and a server (e.g., wikipedia.org) will have all of the following properties: Figure 2: Figure 1 from Automated Testing of Broken Authentication ...

2. System Architecture & Core Working Principles The connection is private (or has confidentiality) because a symmetric-key algorithm is used to encrypt the data transmitted. The keys for this symmetric encryption are generated uniquely for each connection and are based on a shared secret that was negotiated at the start of the session. The server and client negotiate the details of which encryption algorithm and cryptographic keys to use before the first byte of data is transmitted (see below). The negotiation of a shared secret is both secure (the negotiated secret is unavailable to eavesdroppers and cannot be obtained, even by an attacker who places themselves in the middle of the connection) and reliable (no attacker can modify the communications during the negotiation without being detected). The identity of the communicating parties can be authenticated using public-key cryptography. This authentication is required for the server and optional for the client. The connection is reliable (or has integrity) because each message transmitted includes a message integrity check using a message authentication code to prevent undetected loss or alteration of the data during transmission. TLS supports many different methods for exchanging keys, encrypting data, and authenticating message integrity. As a result, secure configuration of TLS involves many configurable parameters, and not all choices provide all of the privacy-related properties described in the list above (see the tables below § Key exchange, § Cipher security, and § Data integrity). Attempts have been made to subvert aspects of the communications security that TLS seeks to provide, and the protocol has been revised several times to address these security threats. Developers of web browsers have repeatedly revised their products to defend against potential security weaknesses after these were discovered (see TLS/SSL support history of web browsers).

In August 1986, the National Security Agency, the National Bureau of Standards, the Defense Communications Agency launched a project, called the Secure Data Network System (SDNS), with the intent of designing the next generation of secure computer communications network and product specifications to be implemented for applications on public and private internets. It was intended to complement the rapidly emerging new OSI internet standards moving forward both in the U.S.

government's GOSIP Profiles and in the huge ITU-ISO JTC1 internet effort internationally. As part of the project, researchers designed a protocol called SP4 (security protocol in layer 4 of the OSI system). This was later renamed the Transport Layer Security Protocol (TLSP) and subsequently published in 1995 as international standard ITU-T X.274|ISO/IEC 10736:1995. Despite the name similarity, this is distinct from today's TLS.

Netscape developed the original SSL protocols, and Taher Elgamal, chief scientist at Netscape Communications from 1995 to 1998, has been described as the "father of SSL". SSL version 1.0 was never publicly released because of serious security flaws in the protocol. Version 2.0, after being released in February 1995 was quickly found to contain a number of security and usability flaws. It used the same cryptographic keys for message authentication and encryption. It had a weak MAC construction that used the MD5 hash function with a secret prefix, making it vulnerable to length extension attacks. It also provided no protection for either the opening handshake or an explicit message close, both of which meant man-in-the-middle attacks could go undetected. Moreover, SSL 2.0 assumed a single service and a fixed domain certificate, conflicting with the widely used feature of virtual hosting in Web servers, so most websites were effectively impaired from using SSL. These flaws necessitated the complete redesign of the protocol to SSL version 3.0. Released in 1996, it was produced by Paul Kocher working with Netscape engineers Phil Karlton and Alan Freier, with a reference implementation by Christopher Allen and Tim Dierks of Certicom. Newer versions of SSL/TLS are based on SSL 3.0. The 1996 draft of SSL 3.0 was published by IETF as a historical document in RFC 6101. SSL 2.0 was deprecated in 2011 by RFC 6176. In 2014, SSL 3.0 was found to be vulnerable to the POODLE attack that affects all block ciphers in SSL; RC4, the only non-block cipher supported by SSL 3.0, is also feasibly broken as used in SSL 3.0. SSL 3.0 was deprecated in June 2015 by RFC 7568.

Added protection against cipher-block chaining (CBC) attacks. The implicit initialization vector (IV) was replaced with an explicit IV. Change in handling of padding errors. Support for IANA registration of parameters. Support for TLS versions 1.0 and 1.1 was widely deprecated by web sites around 2020, disabling access to Firefox versions before 24 and Chromium-based browsers before 29, though third-party fixes can be applied to Netscape Navigator and older versions of Firefox to add TLS 1.2 support.

Figure 3: Broken Authentication Vulnerability | SecureFlag Security Knowledge Base The MD5 and SHA-1 combination in the pseudorandom function (PRF) was replaced with SHA-256, with an option to use cipher suite specified PRFs. The MD5 and SHA-1 combination in the finished message hash was replaced with SHA-256, with an option to use cipher suite specific hash algorithms. However, the size of the hash in the finished message must still be at least 96 bits. The MD5 and SHA-1 combination in the digitally signed element was replaced with a single hash negotiated during handshake, which defaults to SHA-1. Enhancement in the client's and server's ability to specify which hashes and signature algorithms they accept. Expansion of support for authenticated encryption ciphers, used mainly for Galois/Counter Mode (GCM) and CCM mode of Advanced Encryption Standard (AES) encryption. TLS Extensions definition and AES cipher suites were added. All TLS versions were further refined in RFC 6176 in March 2011, removing their backward compatibility with SSL such that TLS sessions never negotiate the use of Secure Sockets Layer (SSL) version 2.0. As of July 2026, there is no formal date for TLS 1.2 to be deprecated which allows for legacy clients. However the use of MD5 and SHA1 hash methods as well as Diffie-Hellman (DH) over a finite field and RSA key exchanges have been deprecated. (RFC 9155, 10015) Separating key agreement and authentication algorithms from the cipher suites Removing support for weak and less-used named elliptic curves Removing support for MD5 and SHA-224 cryptographic hash functions Requiring digital signatures even when a previous configuration is used Integrating HKDF and the semi-ephemeral DH proposal Replacing resumption with PSK and tickets Supporting 1-RTT handshakes and initial support for 0-RTT Mandating perfect forward secrecy, by means of using ephemeral keys during the (EC)DH key agreement Dropping support for many insecure or obsolete features including compression, renegotiation, non-AEAD ciphers, null ciphers, non-PFS key exchange (among which are static RSA and static DH key exchanges), custom DHE groups, EC point format negotiation, Change Cipher Spec protocol, Hello message UNIX time, and the length field AD input to AEAD ciphers Prohibiting SSL or RC4 negotiation for backwards compatibility Integrating use of session hash Deprecating use of the record layer version number and freezing the number for improved backwards compatibility Moving some security-related algorithm details from an appendix to the specification and relegating ClientKeyShare to an appendix Adding the ChaCha20 stream cipher with the Poly1305 message authentication code Adding the Ed25519 and Ed448 digital signature algorithms Adding the x25519 and x448 key exchange protocols Adding support for sending multiple OCSP responses Encrypting all handshake messages after the ServerHello, including server certificate Network Security Services (NSS), the cryptography library developed by Mozilla and used by its web browser Firefox, enabled TLS 1.3 by default in February 2017. TLS 1.3 support was subsequently added — but due to compatibility issues for a small number of users, not automatically enabled — to Firefox 52.0, which was released in March 2017. TLS 1.3 was enabled by default in May 2018 with the release of Firefox 60.0. Google Chrome set TLS 1.3 as the default version for a short time in 2017. It then removed it as the default, due to incompatible middleboxes such as Blue Coat web proxies. The intolerance of the new version of TLS was protocol ossification; middleboxes had ossified the protocol's version parameter. As a result, version 1.3 mimics the wire image of version 1.2. This change occurred very late in the design process, only having been discovered during browser deployment. The discovery of this intolerance also led to the prior version negotiation strategy, where the highest matching version was picked, being abandoned due to unworkable levels of ossification. 'Greasing' an extension point, where one protocol participant claims support for non-existent extensions to ensure that unrecognised-but-actually-existent extensions are tolerated and so to resist ossification, was originally designed for TLS, but it has since been adopted elsewhere. During the IETF 100 Hackathon, which took place in Singapore in 2017, the TLS Group worked on adapting open-source applications to use TLS 1.3. The TLS group was made up of individuals from Japan, United Kingdom, and Mauritius via the cyberstorm.mu team. This work was continued in the IETF 101 Hackathon in London, and the IETF 102 Hackathon in Montreal. wolfSSL enabled the use of TLS 1.3 as of version 3.11.1, released in May 2017. As the first commercial TLS 1.3 implementation, wolfSSL 3.11.1 supported Draft 18 and now supports Draft 28, the final version, as well as many older versions. A series of blogs were published on the performance difference between TLS 1.2 and 1.3. In September 2018, the popular OpenSSL project released version 1.1.1 of its library, in which support for TLS 1.3 was "the headline new feature". Support for TLS 1.3 was added to Secure Channel (schannel) for the GA releases of Windows 11 and Windows Server 2022.

A digital certificate certifies the ownership of a public key by the named subject of the certificate, and indicates certain expected usages of that key. This allows others (relying parties) to rely upon signatures or on assertions made by the private key that corresponds to the certified public key. Keystores and trust stores can be in various formats, such as .pem, .crt, .pfx, .p12 and .jks.

TLS typically relies on a set of trusted third-party certificate authorities to establish the authenticity of certificates. Trust is usually anchored in a list of certificates distributed with user agent software, and can be modified by the relying party. According to Netcraft, who monitors active TLS certificates, the market-leading certificate authority (CA) has been Symantec since the beginning of their survey (or VeriSign before the authentication services business unit was purchased by Symantec).

As of 2015, Symantec accounted for just under a third of all certificates and 44% of the valid certificates used by the 1 million busiest websites, as counted by Netcraft. In 2017, Symantec sold its TLS/SSL business to DigiCert. In an updated report, it was shown that IdenTrust, DigiCert, and Sectigo are the top 3 certificate authorities in terms of market share since May 2019. As a consequence of choosing X.509 certificates, certificate authorities and a public key infrastructure are necessary to verify the relation between a certificate and its owner, as well as to generate, sign, and administer the validity of certificates. While this can be more convenient than verifying the identities via a web of trust, the 2013 mass surveillance disclosures made it more widely known that certificate authorities are a weak point from a security standpoint, allowing man-in-the-middle attacks (MITM) if the certificate authority cooperates (or is compromised). On April 11, 2025, the CA/Browser Forum approved a ballot that will require all public TLS certificate lifespans to gradually reduce to 47 days by 2029. The ballot was proposed by Apple.

3. Software Implementation, Frameworks & Protocols As of March 2025, the latest versions of all major web browsers support TLS 1.2 and 1.3 and have them enabled by default, with the exception of IE 11. TLS 1.0 and 1.1 are disabled by default on the latest versions of all major browsers. Mitigations against known attacks are not enough yet: Mitigations against POODLE attack: some browsers already prevent fallback to SSL 3.0; however, this mitigation needs to be supported by not only clients but also servers. Disabling SSL 3.0 itself, implementation of "anti-POODLE record splitting", or denying CBC ciphers in SSL 3.0 is required. Google Chrome: complete (TLS_FALLBACK_SCSV is implemented since version 33, fallback to SSL 3.0 is disabled since version 39, SSL 3.0 itself is disabled by default since version 40. Support of SSL 3.0 itself was dropped since version 44.) Mozilla Firefox: complete (support of SSL 3.0 itself is dropped since version 39.

SSL 3.0 itself is disabled by default and fallback to SSL 3.0 are disabled since version 34, TLS_FALLBACK_SCSV is implemented since version 35. In ESR, SSL 3.0 itself is disabled by default and TLS_FALLBACK_SCSV is implemented since ESR 31.3.0.) Internet Explorer: partial (only in version 11, SSL 3.0 is disabled by default since April 2015. Version 10 and older are still vulnerable against POODLE.) Opera: complete (TLS_FALLBACK_SCSV is implemented since version 20, "anti-POODLE record splitting", which is effective only with client-side implementation, is implemented since version 25, SSL 3.0 itself is disabled by default since version 27. Support of SSL 3.0 itself will be dropped since version 31.) Safari: complete (only on OS X 10.8 and later and iOS 8, CBC ciphers during fallback to SSL 3.0 is denied, but this means it will use RC4, which is not recommended as well. Support of SSL 3.0 itself is dropped on OS X 10.11 and later and iOS 9.) Mitigation against RC4 attacks: Google Chrome disabled RC4 except as a fallback since version 43. RC4 is disabled since Chrome 48.

Firefox disabled RC4 except as a fallback since version 36. Firefox 44 disabled RC4 by default. Opera disabled RC4 except as a fallback since version 30. RC4 is disabled since Opera 35. Internet Explorer for Windows 7/Server 2008 R2 and for Windows 8/Server 2012 have set the priority of RC4 to lowest and can also disable RC4 except as a fallback through registry settings. Internet Explorer 11 Mobile 11 for Windows Phone 8.1 disable RC4 except as a fallback if no other enabled algorithm works. Edge [Legacy] and IE 11 disable RC4 completely in August 2016. Mitigation against FREAK attack: The Android Browser included with Android 4.0 and older is still vulnerable to the FREAK attack. Internet Explorer 11 Mobile is still vulnerable to the FREAK attack. Google Chrome, Internet Explorer (desktop), Safari (desktop & mobile), and Opera (mobile) have FREAK mitigations in place. Mozilla Firefox on all platforms and Google Chrome on Windows were not affected by FREAK.

BoringSSL, a fork of OpenSSL for Chrome/Chromium and Android as well as other Google applications. Botan, a BSD-licensed cryptographic library written in C++. BSAFE Micro Edition Suite: a multi-platform implementation of TLS written in C using a FIPS-validated cryptographic module BSAFE SSL-J: a TLS library providing both a proprietary API and JSSE API, using FIPS-validated cryptographic module cryptlib: a portable open source cryptography library (includes TLS/SSL implementation) Delphi programmers may use a library called Indy which utilizes OpenSSL or alternatively ICS which supports TLS 1.3 now. GnuTLS: a free implementation (LGPL licensed) Java Secure Socket Extension (JSSE): the Java API and provider implementation (named SunJSSE) LibreSSL: a fork of OpenSSL by OpenBSD project. MatrixSSL: a dual licensed implementation Mbed TLS (previously PolarSSL): A tiny SSL library implementation for embedded devices that is designed for ease of use Network Security Services: FIPS 140 validated open source library OpenSSL: a free implementation (BSD license with some extensions) Rustls, An implementation of TLS 1.3 written in the Rust programming language to ensure memory safety. Schannel: an implementation of SSL and TLS Microsoft Windows as part of its package. Secure Transport: an implementation of SSL and TLS used in OS X and iOS as part of their packages. wolfSSL (previously CyaSSL): Embedded SSL/TLS Library with a strong focus on speed and size. A paper presented at the 2012 ACM conference on computer and communications security showed that many applications used some of these SSL libraries incorrectly, leading to vulnerabilities. According to the authors: "The root cause of most of these vulnerabilities is the terrible design of the APIs to the underlying SSL libraries. Instead of expressing high-level security properties of network tunnels such as confidentiality and authentication, these APIs expose low-level details of the SSL protocol to application developers. As a consequence, developers often use SSL APIs incorrectly, misinterpreting and misunderstanding their manifold parameters, options, side effects, and return values." A protocol downgrade attack (also called a version rollback attack) tricks a web server into negotiating connections with previous versions of TLS (such as SSLv2) that have long since been abandoned as insecure. Previous modifications to the original protocols, like False Start (adopted and enabled by Google Chrome) or Snap Start, reportedly introduced limited TLS protocol downgrade attacks or allowed modifications to the cipher suite list sent by the client to the server. In doing so, an attacker might succeed in influencing the cipher suite selection in an attempt to downgrade the cipher suite negotiated to use either a weaker symmetric encryption algorithm or a weaker key exchange. A paper presented at an ACM conference on computer and communications security in 2012 demonstrated that the False Start extension was at risk: in certain circumstances it could allow an attacker to recover the encryption keys offline and to access the encrypted data. Encryption downgrade attacks can force servers and clients to negotiate a connection using cryptographically weak keys. In 2014, a man-in-the-middle attack called FREAK was discovered affecting the OpenSSL stack, the default Android web browser, and some Safari browsers. The attack involved tricking servers into negotiating a TLS connection using cryptographically weak 512 bit encryption keys. Logjam is a security exploit discovered in May 2015 that exploits the option of using legacy "export-grade" 512-bit Diffie–Hellman groups dating back to the 1990s. It forces susceptible servers to downgrade to cryptographically weak 512-bit Diffie–Hellman groups. An attacker can then deduce the keys the client and server determine using the Diffie–Hellman key exchange.

The DROWN attack is an exploit that attacks servers supporting contemporary SSL/TLS protocol suites by exploiting their support for the obsolete, insecure, SSLv2 protocol to leverage an attack on connections using up-to-date protocols that would otherwise be secure. DROWN exploits a vulnerability in the protocols used and the configuration of the server, rather than any specific implementation error. Full details of DROWN were announced in March 2016, together with a patch for the exploit. At that time, more than 81,000 of the top 1 million most popular websites were among the TLS protected websites that were vulnerable to the DROWN attack.

The authors of the BEAST attack are also the creators of the later CRIME attack, which can allow an attacker to recover the content of web cookies when data compression is used along with TLS. When used to recover the content of secret authentication cookies, it allows an attacker to perform session hijacking on an authenticated web session. While the CRIME attack was presented as a general attack that could work effectively against a large number of protocols, including but not limited to TLS, and application-layer protocols such as SPDY or HTTP, only exploits against TLS and SPDY were demonstrated and largely mitigated in browsers and servers. The CRIME exploit against HTTP compression has not been mitigated at all, even though the authors of CRIME have warned that this vulnerability might be even more widespread than SPDY and TLS compression combined. In 2013 a new instance of the CRIME attack against HTTP compression, dubbed BREACH, was announced. Based on the CRIME attack a BREACH attack can extract login tokens, email addresses or other sensitive information from TLS encrypted web traffic in as little as 30 seconds (depending on the number of bytes to be extracted), provided the attacker tricks the victim into visiting a malicious web link or is able to inject content into valid pages the user is visiting (ex: a wireless network under the control of the attacker). All versions of TLS and SSL are at risk from BREACH regardless of the encryption algorithm or cipher used. Unlike previous instances of CRIME, which can be successfully defended against by turning off TLS compression or SPDY header compression, BREACH exploits HTTP compression which cannot realistically be turned off, as virtually all web servers rely upon it to improve data transmission speeds for users. This is a known limitation of TLS as it is susceptible to chosen-plaintext attack against the application-layer data it was meant to protect.

On October 14, 2014, Google researchers published a vulnerability in the design of SSL 3.0, which makes CBC mode of operation with SSL 3.0 vulnerable to a padding attack (CVE-2014-3566). They named this attack POODLE (Padding Oracle On Downgraded Legacy Encryption). On average, attackers only need to make 256 SSL 3.0 requests to reveal one byte of encrypted messages. Although this vulnerability only exists in SSL 3.0 and most clients and servers support TLS 1.0 and above, all major browsers voluntarily downgrade to SSL 3.0 if the handshakes with newer versions of TLS fail unless they provide the option for a user or administrator to disable SSL 3.0 and the user or administrator does so. Therefore, the man-in-the-middle can first conduct a version rollback attack and then exploit this vulnerability. On December 8, 2014, a variant of POODLE was announced that impacts TLS implementations that do not properly enforce padding byte requirements.

4. Practical Deployment, Analysis & Case Studies Despite the existence of attacks on RC4 that broke its security, cipher suites in SSL and TLS that were based on RC4 were still considered secure prior to 2013 based on the way in which they were used in SSL and TLS. In 2011, the RC4 suite was actually recommended as a workaround for the BEAST attack. New forms of attack disclosed in March 2013 conclusively demonstrated the feasibility of breaking RC4 in TLS, suggesting it was not a good workaround for BEAST. An attack scenario was proposed by AlFardan, Bernstein, Paterson, Poettering and Schuldt that used newly discovered statistical biases in the RC4 key table to recover parts of the plaintext with a large number of TLS encryptions. An attack on RC4 in TLS and SSL that requires 13 × 220 encryptions to break RC4 was unveiled on 8 July 2013 and later described as "feasible" in the accompanying presentation at a USENIX Security Symposium in August 2013. In July 2015, subsequent improvements in the attack make it increasingly practical to defeat the security of RC4-encrypted TLS. As many modern browsers have been designed to defeat BEAST attacks (except Safari for Mac OS X 10.7 or earlier, for iOS 6 or earlier, and for Windows; see § Web browsers), RC4 is no longer a good choice for TLS 1.0. The CBC ciphers which were affected by the BEAST attack in the past have become a more popular choice for protection. Mozilla and Microsoft recommend disabling RC4 where possible.

In February 2015, the use of RC4 cipher suites was officially prohibited in all versions of TLS. On September 1, 2015, Microsoft, Google, and Mozilla announced that RC4 cipher suites would be disabled by default in their browsers (Microsoft Edge [Legacy], Internet Explorer 11 on Windows 7/8.1/10, Firefox, and Chrome) in early 2016. The Heartbleed bug is a serious vulnerability specific to the implementation of SSL/TLS in the popular OpenSSL cryptographic software library, affecting versions 1.0.1 to 1.0.1f. This weakness, reported in April 2014, allows attackers to extract private keys from servers that should normally be protected. The Heartbleed bug allows anyone on the Internet to read the memory of the systems protected by the vulnerable versions of the OpenSSL software. This compromises the secret private keys associated with the public certificates used to identify the service providers and to encrypt the traffic, the names and passwords of the users and the actual content. This allows attackers to eavesdrop on communications, extract data directly from the services and users and to impersonate services and users. The vulnerability is caused by a buffer over-read bug in the OpenSSL software, rather than a defect in the SSL or TLS protocol specification. In September 2014, a variant of Daniel Bleichenbacher's PKCS#1 v1.5 RSA Signature Forgery vulnerability was announced by Intel Security Advanced Threat Research. This attack, dubbed BERserk, is a result of incomplete ASN.1 length decoding of public key signatures in some SSL implementations, and allows a man-in-the-middle attack by forging a public key signature. In February 2015, after media reported the hidden pre-installation of superfish adware on some Lenovo notebooks, a researcher found a trusted root certificate on affected Lenovo machines to be insecure, as the keys could easily be accessed using the company name, Komodia, as a passphrase. The Komodia library was designed to intercept client-side TLS/SSL traffic for parental control and surveillance, but it was also used in numerous adware programs, including Superfish, that were often surreptitiously installed unbeknownst to the computer user. In turn, these potentially unwanted programs installed the corrupt root certificate, allowing attackers to completely control web traffic and confirm false websites as authentic. In May 2016, it was reported that dozens of Danish HTTPS-protected websites belonging to Visa Inc. were vulnerable to attacks allowing hackers to inject malicious code and forged content into the browsers of visitors. The attacks worked because the TLS implementation used on the affected servers incorrectly reused random numbers (nonces) that are intended to be used only once, ensuring that each TLS handshake is unique. In February 2017, an implementation error caused by a single mistyped character in code used to parse HTML created a buffer overflow error on Cloudflare servers. Similar in its effects to the Heartbleed bug discovered in 2014, this overflow error, widely known as Cloudbleed, allowed unauthorized third parties to read data in the memory of programs running on the servers—data that should otherwise have been protected by TLS.

Forward secrecy is a property of cryptographic systems which ensures that a session key derived from a set of public and private keys will not be compromised if one of the private keys is compromised in the future. Without forward secrecy, if the server's private key is compromised, not only will all future TLS-encrypted sessions using that server certificate be compromised, but also any past sessions that used it as well (provided that these past sessions were intercepted and stored at the time of transmission). An implementation of TLS can provide forward secrecy by requiring the use of ephemeral Diffie–Hellman key exchange to establish session keys, and some notable TLS implementations do so exclusively: e.g., Gmail and other Google HTTPS services that use OpenSSL. However, many clients and servers supporting TLS (including browsers and web servers) are not configured to implement such restrictions. In practice, unless a web service uses Diffie–Hellman key exchange to implement forward secrecy, all of the encrypted web traffic to and from that service can be decrypted by a third party if it obtains the server's master (private) key; e.g., by means of a court order. Even where Diffie–Hellman key exchange is implemented, server-side session management mechanisms can impact forward secrecy. The use of TLS session tickets (a TLS extension) causes the session to be protected by AES128-CBC-SHA256 regardless of any other negotiated TLS parameters, including forward secrecy ciphersuites, and the long-lived TLS session ticket keys defeat the attempt to implement forward secrecy. Stanford University research in 2014 also found that of 473,802 TLS servers surveyed, 82.9% of the servers deploying ephemeral Diffie–Hellman (DHE) key exchange to support forward secrecy were using weak Diffie–Hellman parameters. These weak parameter choices could potentially compromise the effectiveness of the forward secrecy that the servers sought to provide. Since late 2011, Google has provided forward secrecy with TLS by default to users of its Gmail service, along with Google Docs and encrypted search, among other services. Since November 2013, Twitter has provided forward secrecy with TLS to users of its service. As of August 2019, about 80% of TLS-enabled websites are configured to use cipher suites that provide forward secrecy to most web browsers.

TLS interception (or HTTPS interception if applied particularly to that protocol) is the practice of intercepting an encrypted data stream in order to decrypt it, read and possibly manipulate it, and then re-encrypt it and send the data on its way again. This is done by way of a "transparent proxy": the interception software terminates the incoming TLS connection, inspects the HTTP plaintext, and then creates a new TLS connection to the destination. TLS/HTTPS interception is used as an information security measure by network operators in order to be able to scan for and protect against the intrusion of malicious content into the network, such as computer viruses and other malware. Such content could otherwise not be detected as long as it is protected by encryption, which is increasingly the case as a result of the routine use of HTTPS and other secure protocols. A significant drawback of TLS/HTTPS interception is that it introduces new security risks of its own. One notable limitation is that it provides a point where network traffic is available unencrypted thus giving attackers an incentive to attack this point in particular in order to gain access to otherwise secure content. The interception also allows the network operator, or persons who gain access to its interception system, to perform man-in-the-middle attacks against network users. A 2017 study found that "HTTPS interception has become startlingly widespread, and that interception products as a class have a dramatically negative impact on connection security".

When the connection starts, the record encapsulates a "control" protocol – the handshake messaging protocol (content type 22). This protocol is used to exchange all the information required by both sides for the exchange of the actual application data by TLS. It defines the format of messages and the order of their exchange. These may vary according to the demands of the client and server – i.e., there are several possible procedures to set up the connection. This initial exchange results in a successful TLS connection (both parties ready to transfer application data with TLS) or an alert message (as specified below).

Negotiation phase: A client sends a ClientHello message specifying the highest TLS protocol version it supports, a random number, a list of suggested cipher suites and suggested compression methods. If the client is attempting to perform a resumed handshake, it may send a session ID. If the client can use Application-Layer Protocol Negotiation, it may include a list of supported application protocols, such as HTTP/2. The server responds with a ServerHello message, containing the chosen protocol version, a random number, cipher suite and compression method from the choices offered by the client. To confirm or allow resumed handshakes the server may send a session ID. The chosen protocol version should be the highest that both the client and server support. For example, if the client supports TLS version 1.1 and the server supports version 1.2, version 1.1 should be selected; version 1.2 should not be selected. The server sends its Certificate message (depending on the selected cipher suite, this may be omitted by the server). The server sends its ServerKeyExchange message (depending on the selected cipher suite, this may be omitted by the server). This message is sent for all DHE, ECDHE and DH_anon cipher suites. The server sends a ServerHelloDone message, indicating it is done with handshake negotiation. The client responds with a ClientKeyExchange message, which may contain a PreMasterSecret, public key, or nothing. (Again, this depends on the selected cipher.) This PreMasterSecret is encrypted using the public key of the server certificate. The client and server then use the random numbers and PreMasterSecret to compute a common secret, called the "master secret". All other key data (session keys such as IV, symmetric encryption key, MAC key) for this connection is derived from this master secret (and the client- and server-generated random values), which is passed through a carefully designed pseudorandom function. The client now sends a ChangeCipherSpec record, essentially telling the server, "Everything I tell you from now on will be authenticated (and encrypted if encryption parameters were present in the server certificate)." The ChangeCipherSpec is itself a record-level protocol with content type of 20. The client sends an authenticated and encrypted Finished message, containing a hash and MAC over the previous handshake messages. The server will attempt to decrypt the client's Finished message and verify the hash and MAC. If the decryption or verification fails, the handshake is considered to have failed and the connection should be terminated. Finally, the server sends a ChangeCipherSpec, telling the client, "Everything I tell you from now on will be authenticated (and encrypted, if encryption was negotiated)." The server sends its authenticated and encrypted Finished message. The client performs the same decryption and verification procedure as the server did in the previous step. Application phase: at this point, the "handshake" is complete and the application protocol is enabled, with content type of 23. Application messages exchanged between client and server will also be authenticated and optionally encrypted exactly like in their Finished message. Otherwise, the content type will return 25 and the client will not authenticate.

Negotiation Phase: A client sends a ClientHello message specifying the highest TLS protocol version it supports, a random number, a list of suggested cipher suites and compression methods. The server responds with a ServerHello message, containing the chosen protocol version, a random number, cipher suite and compression method from the choices offered by the client. The server may also send a session id as part of the message to perform a resumed handshake. The server sends its Certificate message (depending on the selected cipher suite, this may be omitted by the server). The server sends its ServerKeyExchange message (depending on the selected cipher suite, this may be omitted by the server). This message is sent for all DHE, ECDHE and DH_anon ciphersuites.[1] The server sends a CertificateRequest message, to request a certificate from the client. The server sends a ServerHelloDone message, indicating it is done with handshake negotiation.

The client responds with a Certificate message, which contains the client's certificate, but not its private key. The client sends a ClientKeyExchange message, which may contain a PreMasterSecret, public key, or nothing. (Again, this depends on the selected cipher.) This PreMasterSecret is encrypted using the public key of the server certificate. The client sends a CertificateVerify message, which is a signature over the previous handshake messages using the client's certificate's private key. This signature can be verified by using the client's certificate's public key. This lets the server know that the client has access to the private key of the certificate and thus owns the certificate. The client and server then use the random numbers and PreMasterSecret to compute a common secret, called the "master secret". All other key data ("session keys") for this connection is derived from this master secret (and the client- and server-generated random values), which is passed through a carefully designed pseudorandom function. The client now sends a ChangeCipherSpec record, essentially telling the server, "Everything I tell you from now on will be authenticated (and encrypted if encryption was negotiated). "The ChangeCipherSpec is itself a record-level protocol and has type 20 and not 22. Finally, the client sends an encrypted Finished message, containing a hash and MAC over the previous handshake messages. The server will attempt to decrypt the client's Finished message and verify the hash and MAC. If the decryption or verification fails, the handshake is considered to have failed and the connection should be torn down. Finally, the server sends a ChangeCipherSpec, telling the client, "Everything I tell you from now on will be authenticated (and encrypted if encryption was negotiated)." The server sends its own encrypted Finished message. The client performs the same decryption and verification procedure as the server did in the previous step.

Application phase: at this point, the "handshake" is complete and the application protocol is enabled, with content type of 23. Application messages exchanged between client and server will also be encrypted exactly like in their Finished message. Negotiation phase: A client sends a ClientHello message specifying the highest TLS protocol version it supports, a random number, a list of suggested cipher suites and compression methods. Included in the message is the session id from the previous TLS connection. The server responds with a ServerHello message, containing the chosen protocol version, a random number, cipher suite and compression method from the choices offered by the client. If the server recognizes the session id sent by the client, it responds with the same session id. The client uses this to recognize that a resumed handshake is being performed. If the server does not recognize the session id sent by the client, it sends a different value for its session id. This tells the client that a resumed handshake will not be performed. At this point, both the client and server have the "master secret" and random data to generate the key data to be used for this connection. The server now sends a ChangeCipherSpec record, essentially telling the client, "Everything I tell you from now on will be encrypted." The ChangeCipherSpec is itself a record-level protocol and has type 20 and not 22. Finally, the server sends an encrypted Finished message, containing a hash and MAC over the previous handshake messages. The client will attempt to decrypt the server's Finished message and verify the hash and MAC. If the decryption or verification fails, the handshake is considered to have failed and the connection should be torn down. Finally, the client sends a ChangeCipherSpec, telling the server, "Everything I tell you from now on will be encrypted." The client sends its own encrypted Finished message. The server performs the same decryption and verification procedure as the client did in the previous step. Application phase: at this point, the "handshake" is complete and the application protocol is enabled, with content type of 23. Application messages exchanged between client and server will also be encrypted exactly like in their Finished message.

5. Performance Evaluation & Extended Technical Observations Content Type: 8 bits This field identifies the Record Layer Protocol Type contained in this record. Legacy version: 16 bits This field identifies the major and minor version of TLS prior to TLS 1.3 for the contained message. For a ClientHello message, this need not be the highest version supported by the client. For TLS 1.3 and later, this must be set to 0x0303 and application must send supported versions in an extra message extension block.

Length: 16 bits; Length < 214 The length of Protocol message(s), MAC and Padding fields combined. The length should not exceed 214 bytes (16 KiB). Protocol message(s): variable One or more messages identified by the Protocol field. Note that this field may be encrypted depending on the state of the connection. The length (in bytes) of all messages is indicated by the letter m. Message Authentication Code (MAC): 16, 20, or 32 bytes (optional) A message authentication code computed over the Protocol message(s) field, with additional key material included. 32 bytes for the SHA-256-based HMAC, 20 bytes for the SHA-1-based HMAC, 16 bytes for the MD5-based HMAC. Note that this field may be encrypted, or not included entirely, depending on the state of the connection. The length (in bytes) of the MAC is indicated by the letter q. Padding: variable (optional) Padding is only added when needed. No MAC or Padding fields can be present at end of TLS records before all cipher algorithms and parameters have been negotiated and handshaked and then confirmed by sending a CipherStateChange record (see below) for signalling that these parameters will take effect in all further records sent by the same peer.

Content Type: 8 bits; == 22 This field indicates the Handshake Protocol Type. Message Type: 8 bits This field identifies the handshake message type. Handshake Message Data Length: 24 bits This is a 3-byte field indicating the length of the handshake data, not including the header. Handshake Message: variable Data of the handshake message itself. Note that multiple handshake messages may be combined within one record.

Content Type: 8 bits; == 21 This field indicates the Alert Protocol Type. Length: 16 bits; == 2 The length of the rest of fields, which is 2. Level: 8 bits This field identifies the level of alert. If the level is fatal, the sender should close the session immediately. Otherwise, the recipient may decide to terminate the session itself, by sending its own fatal alert and closing the session itself immediately after sending it. The use of Alert records is optional, however if it is missing before the session closure, the session may be resumed automatically (with its handshakes). Normal closure of a session after termination of the transported application should preferably be alerted with at least the Close notify Alert type (with a simple warning level) to prevent such automatic resume of a new session. Signalling explicitly the normal closure of a secure session before effectively closing its transport layer is useful to prevent or detect attacks (like attempts to truncate the securely transported data, if it intrinsically does not have a predetermined length or duration that the recipient of the secured data may expect).

Content Type: 8 bits; == 20 This field indicates the ChangeCipherSpec Protocol Type. Length: 16 bits; == 1 The length of the rest of fields, which is 1. CCS Protocol Type: 8 bits This field identifies the CCS Protocol type. There is currently only one. Content Type: 8 bits; == 23 This field identifies the Application Protocol Type. Length: 16 bits; Length < 214 The length of Application Data, MAC and Padding fields combined. The length should not exceed 214 bytes (16 KiB). Application Data: variable Data of the application. The length (in bytes) of the data is indicated by the letter m. Message Authentication Code (MAC): 16, 20, or 32 bytes (optional) A message authentication code computed over the Application Data field. 32 bytes for the SHA-256-based HMAC, 20 bytes for the SHA-1-based HMAC, 16 bytes for the MD5-based HMAC. The length (in bytes) of the MAC is indicated by the letter q. Padding: variable (optional) The last byte contains the padding length.

Harvested Online Documentation & Reference Sources • https://en.wikipedia.org/wiki/WebAuthn • https://en.wikipedia.org/wiki/Transport%20Layer%20Security • https://en.wikipedia.org/wiki/List%20of%20computing%20and%20IT%20abbreviations