Santa Cruz CA 95060-1950 US zenomt@zenomt.com https://zenomt.zenomt.com/card.ttl#me

Independent Submission This memo describes a protocol framework for HTTP clients to obtain bearer tokens for accessing restricted resources, where in some applications the client may not have prior knowledge of, or a direct relationship with, the resource server's authorization infrastructure (such as in decentralized identity systems). Semi-concrete applications of the framework using proof-of-possession and TLS client certificate mechanisms are also described.

Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at . Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 27 February 2021.

Copyright Notice Copyright (c) 2020 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents () in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document.

Table of Contents

• .  Introduction
  • .  Motivation
    • .  Use Cases
  • .  Terminology
• .  General Framework
  • .  Nonce Considerations
  • .  Common Token Response
  • .  Common Mechanism Flow
• .  Proof-of-Possession Mechanism
  • .  Proof Token
  • .  Proof-of-Possession API
  • .  Proof-of-Possession Example
• .  TLS Client Certificate Mechanism
  • .  Client Certificate API
  • .  Client Certificate Example
• .  IANA Considerations
• .  Security Considerations
• .  References
  • .  Normative References
  • .  Informative References
• Author's Address

Introduction This memo describes a general protocol framework for HTTP clients to obtain bearer tokens () from a resource server's authorization service in order to access protected resources on the server. This framework is especially intended for systems (such as decentralized identity systems like , and decentralized social or mashup data systems like the Solid project) where the client might not have prior knowledge of, or a preexisting direct relationship with, the authorization service for the resource server; however, it can be applied in other use cases as well. The protocol includes a method for the client to discover the nature(s) of principals (such as identities, capabilities, sender-constrained access tokens, or verifiable credentials) that the server expects to interact with, and methods for the client to discover the API endpoint URIs for multiple potential mechanisms for obtaining bearer tokens. The framework is constructed to mitigate man-in-the-middle token-stealing attacks. This memo defines two mechanisms within the framework for a client to obtain a bearer token: one using a cryptographic proof-of-possession, and one using TLS client certificates. These mechanisms retain generality, and must be further refined in other specifications according to the application and the nature of the principals expected by the servers. Other mechanisms within the framework are also possible.

Motivation This work was originally motivated by a desire to address security, semantic, and operational shortcomings in an experimental, decentralized, application-layer authentication scheme for the Solid project that was based on , OpenID Connect, and proof-of-possession key semantics. An explicit goal of the solution is to leverage the benefits of bearer tokens for accessing restricted resources:

• The token can encapsulate (by direct encoding or by reference) exactly and only the implementation-specific and deployment-specific properties needed to make access control decisions in the resource server;
• The effort (including computational, cryptographic, and network) required to establish a client's identity and authorizations can be done once by the client and the authorization service, compiled to a token, and this effort amortized over many requests to the same resource server, with simple revalidation and lifetime semantics that can be influenced by both parties; specifically:
  • The server's authorization system chooses an expiration period for the token, and can also revoke it at any time, to cause a reauthentication and revalidation;
  • The client can forget the token at any time and acquire a new one to cause a reauthentication and revalidation; this can be particularly advantageous if the client acquires new privileges, authorizations, or endorsements that might otherwise be subject to unknown caching policies in an access controller;
• The representation of the token can be optimized for network transmission and for decoding, verification, and processing according to the server's implementation;
• HTTP header compression schemes such as HPACK can reduce network resource consumption when a token is reused for multiple requests in the same origin.

As work progressed, a general form emerged that could address multiple use cases beyond the original motivator.

Use Cases It is envisioned that the framework described in this memo can be used in at least the following cases, with appropriate further specification, to realize the benefits listed above:

• Decentralized identity systems such as WebID and Decentralized Identifiers;
• Centralized or decentralized authorization systems based on Verifiable Credentials;
• Authenticated access to a multitude of decentralized, uncoordinated resource servers, such as for social or mashup data applications;
• Identity systems based on aspects of a TLS client certificate, without requiring use of that certificate for all accesses to a resource server (particularly in browser-based applications, to allow selective unauthenticated access to non-protected resources within the limitations of negotiating client certificates in TLS);
• Obtaining an audience-constrained bearer token given a sender-constrained access credential or capability issued by a central authority;
• Obtaining an audience-constrained bearer token in a centralized, federated, or confederated identity system given an identity bound with a pre-shared public key.

This list of use cases should not be construed as exhaustive or limiting. Other effective applications of this framework are possible.

Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only when, they appear in all capitals, as shown here. The term "bearer token" in this document has the meaning described in . The term "protection space" in this document has the meaning described in .

General Framework The server challenges an unauthenticated client () with an HTTP 401 response, including a WWW-Authenticate response header with the Bearer auth-scheme (), and comprising parameters including how to use one or more token acquisition mechanisms. The client examines the challenge and determines which mechanisms, if any, it is able to use to acquire a bearer token. If possible, the client uses a compatible mechanism, including attributes of the original request and the challenge, to request a bearer token. The token will have a stated lifetime and will be valid for accesses within the same protection space as the original request, until the token expires or is revoked. A WWW-Authenticate challenge for any mechanism includes at least these auth-params:

scope

REQUIRED: A space-delimited list of case-sensitive strings, each a well-known or server-defined value indicating the nature(s) of the principal expected to be used when requesting a bearer token. To avoid ambiguity, server-defined scopes SHOULD be URIs.

nonce

REQUIRED: An opaque (to the client) string to be included unmodified when requesting a bearer token. See for considerations on constructing the challenge nonce.

error

If present, a reason code indicating that the request had a problem other than not presenting an access token. The following reason codes are initially defined:

invalid_token

A bearer token was presented, but it was expired, revoked, or otherwise not recognized as valid.

proof_required

An access token requiring proof-of-possession of a key (but potentially otherwise valid) was presented.

Additionally, one or more mechanism-specific auth-params are included in the challenge to indicate the availability of that mechanism and its unique parameters (usually the URI at which to use the mechanism). This memo defines two mechanism-specific auth-params:

token_pop_endpoint

If present, the Proof-of-Possession mechanism is available. The parameter value is the URI at which to exchange a proof-of-possession for a bearer token.

client_cert_endpoint

If present, the TLS Client Certificate mechanism is available. The parameter value is the URI at which to request a bearer token.

The challenge can include other auth-params (such as realm), including ones for other mechanisms. Unrecognized auth-params SHOULD be ignored. If a request is made for a resource within a protection space and that request includes an Authorization header with an invalid Bearer token, the resource server SHOULD reply with an HTTP 401 response and WWW-Authenticate header as above, even if processing the request doesn't otherwise require authorization. This is to allow a client to obtain a fresh bearer token proactively (for example, before the current token expires, to avoid delaying a real request by the user).

Nonce Considerations The nonce in the WWW-Authenticate challenge SHOULD have the following properties:

• Be cryptographically strong and unguessable;
• Be recognizable when returned in a token request as having been issued for this protection space (for example, by recording the nonce in a database, or including a cryptographic signature);
• Be valid for a limited (short) time;
• Be redeemable at most once;
• Be coupled to the original request URI in a recognizable way.

Common Token Response It is anticipated that most mechanisms (especially ones that use an HTTP API) will respond to a token request using a common response format. Both of the mechanisms described in this memo use the common format described in this section, which is substantially the same as the format described in . A successful common response is an HTTP 200 response with Content-Type application/json, and having a response body in JSON format encoding a JSON object with at least the following members:

access_token

An opaque (to the client) string; a bearer access token () which can be used for requests in the same protection space as the original request;

expires_in

The number of seconds from the Date of this response after which the access_token will no longer be valid;

token_type

A case-insensitive string identifying the kind of token returned in this response. This value MUST be Bearer.

If there is a problem with the request, the response SHALL be an HTTP 400 response with Content-Type application/json, and having a response body in JSON format encoding a JSON object with at least an error member, and others as appropriate, whose keys and values are defined in . Additional members MAY be included in a successful or unsuccessful response object depending on the scope(s) from the challenge, the mechanism used, and the implementation. Unrecognized response object members SHOULD be ignored.

Common Mechanism Flow It is anticipated that most mechanisms will comprise a simple mechanism-specific API endpoint and respond with a Common Response. The abstract flow for a client to acquire a bearer token in the common way is illustrated in .

Common Protocol Flow Sequence Diagram Client Mechanism Endpoint Resource Server | | | |-- request URI ------------------------------------------->| |<------------------------------ 401 Bearer nonce, scope, --| | | endpoints | |determine compatibility, | | |prepare token request | | |-- POST token request------->| | | |validate request, | | |issue token | |<--------- Common Response --| | | | | | | |-- request URI with access_token ------------------------->| | validate & translate token,| | apply access controls| | | |<--------------------------------------- answer resource --|

Note that the "validate request" step can involve complex operations and include fetching supplemental information from external sources, depending on the semantics of the mechanism, scopes, and principal.

Proof-of-Possession Mechanism The client recognizes the availability of, and its compatibility with, this mechanism, by recognizing combinations of challenge scopes with which it is compatible, the presence of the token_pop_endpoint, and control of an appropriate principal having proof-of-possession semantics (for example, an access token bound to a proof-of-possession key, or a JSON Web Token (JWT) with a cnf claim ) and compatibility with the same combination of challenge scopes. The client constructs and signs a proof-token . The client sends the proof-token to the token_pop_endpoint API URI with HTTP POST . The API endpoint validates the request including the proof-token, and if appropriate, it responds with a bearer token.

Proof Token The proof-token is a JWT, with a signature proving possesion of the key bound to the client's principal, and having the following claims:

sub

REQUIRED: The client's principal (having proof-of-possession semantics and compatible with a combination of the challenge scopes);

aud

REQUIRED: The absolute URI (), including scheme, authority (host and optional port), path, and query, but not including fragment identifier, corresponding to the original request that resulted in the HTTP 401 challenge; if this claim is an array, it MUST have exactly one element;

nonce

REQUIRED: The nonce from the WWW-Authenticate challenge;

jti

RECOMMENDED: Use of this claim is recommended so that the client can salt the proof-token's signature; the verifier can ignore this claim, if present;

exp

OPTIONAL: If present, this claim MUST NOT be after the expiration time of the sub (if it has one), and MUST NOT be before the current time on the verifier; ordinarily the validity of the nonce is sufficient to establish not-before and not-after constraints on the proof, so this claim isn't usually necessary (and clocks on end-user devices, where proof-tokens are likely to be generated, are notoriously inaccurate). The issuer MAY take the expiration periods of the proof-token and the sub into account when determining the expiration period of the bearer token it issues, but it is not required to do so and is free to issue bearer tokens with any expiration period.

Additional claims can appear in the proof-token according to, and conditioned on, the semantics of the scope(s). Unrecognized or incompatible claims SHOULD be ignored.

Proof-of-Possession API This API endpoint is implemented by the authorization server () for the protection space of the original request. The client uses this API by making an HTTP POST request to the token_pop_endpoint URI. The request body has Content-Type application/x-www-form-urlencoded and includes at least the following parameter:

proof_token

REQUIRED: A proof-token as described above.

Additional parameters can be sent according to, and conditioned on, the semantics of the scope(s). Unrecognized or incompatible parameters SHOULD be ignored. The authorization server verifies the request:

1. Parse the proof_token parameter and find its claims;
2. Verify that the proof_token's signature matches the proof-of-possession key associated with the sub claim, and that it hasn't expired;
3. Verify that the aud claim is an absolute URI for a resource in a protection space for which this endpoint is responsible;
4. Verify the nonce claim (for example, by confirming that it was really issued by this system and not too far in the past, that it hasn't been redeemed yet, and that it was issued for a request for the aud claim);
5. Verify the validity and authenticity of the sub claim according to its kind and the semantics of the relevant scope(s);
6. Perform any other processing, verification, and validation appropriate to the relevant scope(s), additional claims, or additional parameters.

If the request is verified, the authorization server issues a bearer access_token valid for the protection space of the original request and for a limited time. The authorization server responds using the common response format ().

Proof-of-Possession Example Note: This section is not normative. A client (for example, an in-browser application working on behalf of a user) attempts an HTTP request to a resource server for an access-restricted URI initially without presenting any special credentials: GET /some/restricted/resource HTTP/1.1 Host: www.example Origin: https://app.example The resource server does not allow this request without authorization. It generates an unguessable, opaque nonce that the server will be able to later recognize as having generated. The server responds with an HTTP 401 Unauthorized message, and includes the protection space identifier (realm), the nonce, the appropriate scopes, and at least the token_pop_endpoint in the WWW-Authenticate response header with the Bearer method. The server also includes an HTML response body to allow the user to perform a first-party login using another method, for cases where the resource was navigated to directly in the browser: HTTP/1.1 401 Unauthorized WWW-Authenticate: Bearer realm="/auth/", scope="webid openid", nonce="j16C4SOLQWFor3VYUtZWnrUr5AG5uwDF7q9RFsDk", token_pop_endpoint="/auth/webid-pop", client_cert_endpoint="https://webid-tls.example/auth/webid-tls" Access-Control-Allow-Origin: https://app.example Access-Control-Expose-Headers: WWW-Authenticate Date: Mon, 6 May 2019 01:48:48 GMT Content-type: text/html <html>Human first-party login page...</html> The client recognizes the response as compatible with this mechanism by recognizing the scheme as Bearer, compatible scopes (in this example, openid and webid), and the presence of the nonce and the token_pop_endpoint. The client controls a principal appropriate to the scopes (in this example, a JWT substantially similar to an OpenID Connect ID Token and containing a confirmation key) and determines to use the proof-of-possession mechanism. The client creates a new proof-token JWT as described above (), setting its aud claim to the absolute URI of the original request, the nonce claim to the nonce parameter from the WWW-Authenticate response header, the sub claim to its ID Token, includes other claims as appropriate to the scopes (iss in this example), and signs this proof-token with the proof-of-possession key bound to its principal and with a signing algorithm compatible with the signing key and the scopes: { "typ": "JWT", "alg": "RS256" } . { "sub": "eyJhbGciOiJ...", "aud": "https://www.example/some/restricted/resource", "nonce": "j16C4SOLQWFor3VYUtZWnrUr5AG5uwDF7q9RFsDk", "jti": "1C49A92C-C260-4F76-9D7B-E81AE13037B8", "iss": "https://app.example/oauth/code" } . RS256-signature-here The client sends a request to the token_pop_endpoint URI and includes the proof-token: POST /auth/webid-pop Host: www.example Origin: https://app.example Content-type: application/x-www-form-urlencoded proof_token=eyJ0eXAiOiJKV1QiCg... The token_pop_endpoint verifies the request as described in , determines that the request is good, and issues a bearer token: HTTP/1.1 200 Content-type: application/json; charset=utf-8 Cache-control: no-cache, no-store Pragma: no-cache Access-Control-Allow-Origin: https://app.example Date: Mon, 6 May 2019 01:48:50 GMT { "access_token": "RPAOmgrWb5wD7DzloDjZ7Ain", "expires_in": 1800, "token_type": "Bearer" } The client can now use the access_token in an Authorization header for requests to resources in the same protection space as the original request until the access token expires or is revoked: GET /some/restricted/resource HTTP/1.1 Host: www.example Origin: https://app.example Authorization: Bearer RPAOmgrWb5wD7DzloDjZ7Ain The server validates and translates the bearer token in its implementation-specific way, and makes a determination whether to grant the requested access.

TLS Client Certificate Mechanism The client recognizes the availability of, and its compatibility with, this mechanism, by recognizing combinations of challenge scopes with which it is compatible, the presence of the client_cert_endpoint and the nonce, and either direct control of an appropriate TLS client certificate and its signing key, or in the case of browser-based Javascript applications, an assumption that such a certificate is configured into the browser and that it will be selected by the user. The client constructs and sends a token request to the client_cert_endpoint API URI with HTTP POST, using its TLS client certificate. The API endpoint validates the request, including aspects of the client certificate, and if appropriate, it responds with a bearer token.

Client Certificate API This API endpoint is implemented by the authorization server for the protection space of the original request. The client uses this API by making an HTTP POST request to the client_cert_endpoint URI. The request body has Content-Type application/x-www-form-urlencoded and includes at least the following parameters:

uri

REQUIRED: The absolute URI, including scheme, authority (host and optional port), path, and query, but not including fragment identifier, corresponding to the original request that resulted in the HTTP 401 response;

nonce

REQUIRED: The nonce from the WWW-Authenticate challenge.

Additional parameters can be sent according to, and conditioned on, the semantics of the scope(s). Unrecognized or incompatible parameters SHOULD be ignored. A TLS client certificate is REQUIRED when communicating with this API endpoint. That means the origin of this API endpoint will probably be different from that of the original request URI so that the server can request a client certificate in a distinct TLS connection handshake (). The authorization server verifies the request:

1. Verify that uri is an absolute URI and is in a protection space for which this endpoint is responsible;
2. Verify the nonce (for example, confirming that it was really generated by this system, not too far in the past, that it hasn't been redeemed yet, and if possible that it corresponds to a request for uri);
3. Verify the validity and authenticity of the client certificate (beyond those validations required for the TLS connection) according to the semantics of the relevant scope(s);
4. Perform any other processing, verification, and validation appropriate to the relevant scope(s) or additional parameters.

If the request is acceptable, the authorization server issues a bearer access_token valid for the protection space of the original request and for a limited time. The authorization server responds using the common response format.

Client Certificate Example Note: This section is not normative. A client (for example, an in-browser application working on behalf of a user) attempts an HTTP request to a resource server for an access-restricted URI initially without presenting any special credentials: GET /some/restricted/resource HTTP/1.1 Host: www.example Origin: https://app.example The resource server does not allow this request without authorization. It generates an unguessable, opaque nonce that the authorization server will be able to later recognize as having generated. The server responds with an HTTP 401 Unauthorized message, and includes the protection space identifier (realm), the nonce, the appropriate scopes, and at least the client_cert_endpoint in the WWW-Authenticate response header with the Bearer method. The server also includes an HTML response body to allow the user to perform a first-party login using another method, for cases where the resource was navigated to directly in the browser: HTTP/1.1 401 Unauthorized WWW-Authenticate: Bearer realm="/auth/", scope="webid openid", nonce="j16C4SOLQWFor3VYUtZWnrUr5AG5uwDF7q9RFsDk", token_pop_endpoint="/auth/webid-pop", client_cert_endpoint="https://webid-tls.example/auth/webid-tls" Access-Control-Allow-Origin: https://app.example Access-Control-Expose-Headers: WWW-Authenticate Date: Mon, 6 May 2019 01:48:48 GMT Content-type: text/html <html>Human first-party login page...</html> The client recognizes the response as compatible with this mechanism by recognizing the scheme as Bearer, compatible scopes (in this example, webid), and the presence of the nonce and the client_cert_endpoint. The client determines to use the client certificate mechanism (for example, by being configured by the user to do so when available, with the assumption the user will choose an appropriate certificate when prompted by the browser). The client sends, using its TLS client certificate, a token request to the client_cert_endpoint URI and includes the required parameters: POST /auth/webid-tls HTTP/1.1 Host: webid-tls.example Origin: https://app.example Content-type: application/x-www-form-urlencoded uri=https://www.example/some/restricted/resource &nonce=j16C4SOLQWFor3VYUtZWnrUr5AG5uwDF7q9RFsDk The client_cert_endpoint verifies the request as described in (in this example, with scope webid, the validation and processing steps further comprise establishing and validating the user's WebID according to ). The endpoint determines that the request is good, and issues a bearer token: HTTP/1.1 200 Content-type: application/json; charset=utf-8 Cache-control: no-cache, no-store Pragma: no-cache Access-Control-Allow-Origin: https://app.example Date: Mon, 6 May 2019 01:48:50 GMT { "access_token": "RPAOmgrWb5wD7DzloDjZ7Ain", "expires_in": 1800, "token_type": "Bearer" } The client can now use the access_token in an Authorization header for requests to resources in the same protection space as the original request until the bearer token expires or is revoked: GET /some/restricted/resource HTTP/1.1 Host: www.example Origin: https://app.example Authorization: Bearer RPAOmgrWb5wD7DzloDjZ7Ain The server validates and translates the bearer token in its implementation-specific way, and makes a determination whether to grant the requested access.

IANA Considerations TBD. Mechanism parameters "token_pop_endpoint" and "client_cert_endpoint" for auth-scheme "Bearer".

Security Considerations When using the Proof-of-Possession mechanism, the scope designer should carefully consider whether additional information should go in the proof-token (which would therefore be signed) or can be POST parameters (which would not be signed). The safe choice (which therefore SHOULD be the default) is to include any additional information in the proof-token. Bearer tokens can be shared freely with other parties by an application. Therefore, a bearer token obtained with the TLS Client Certificate mechanism MUST NOT be construed to carry the same weight when authenticating an HTTP request as if the client used the corresponding client certificate for the request's connection. However, particularly for browser-based applications where the application and the resource server(s) are not associated with each other, the user typically doesn't audit the data being sent in HTTP requests (even when a client certificate is used), so the portion of the application running in the browser could be receiving data from anywhere else and sending it over HTTP using the user's client certificate anyway. Security considerations specific to challenge scopes are beyond the purview of this memo.

References Normative References In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. A Uniform Resource Identifier (URI) is a compact sequence of characters that identifies an abstract or physical resource. This specification defines the generic URI syntax and a process for resolving URI references that might be in relative form, along with guidelines and security considerations for the use of URIs on the Internet. The URI syntax defines a grammar that is a superset of all valid URIs, allowing an implementation to parse the common components of a URI reference without knowing the scheme-specific requirements of every possible identifier. This specification does not define a generative grammar for URIs; that task is performed by the individual specifications of each URI scheme. [STANDARDS-TRACK] The OAuth 2.0 authorization framework enables a third-party application to obtain limited access to an HTTP service, either on behalf of a resource owner by orchestrating an approval interaction between the resource owner and the HTTP service, or by allowing the third-party application to obtain access on its own behalf. This specification replaces and obsoletes the OAuth 1.0 protocol described in RFC 5849. [STANDARDS-TRACK] This specification describes how to use bearer tokens in HTTP requests to access OAuth 2.0 protected resources. Any party in possession of a bearer token (a "bearer") can use it to get access to the associated resources (without demonstrating possession of a cryptographic key). To prevent misuse, bearer tokens need to be protected from disclosure in storage and in transport. [STANDARDS-TRACK] The Hypertext Transfer Protocol (HTTP) is a stateless application- level protocol for distributed, collaborative, hypermedia information systems. This document defines the HTTP Authentication framework. JSON Web Token (JWT) is a compact, URL-safe means of representing claims to be transferred between two parties. The claims in a JWT are encoded as a JSON object that is used as the payload of a JSON Web Signature (JWS) structure or as the plaintext of a JSON Web Encryption (JWE) structure, enabling the claims to be digitally signed or integrity protected with a Message Authentication Code (MAC) and/or encrypted. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. JavaScript Object Notation (JSON) is a lightweight, text-based, language-independent data interchange format. It was derived from the ECMAScript Programming Language Standard. JSON defines a small set of formatting rules for the portable representation of structured data. This document removes inconsistencies with other specifications of JSON, repairs specification errors, and offers experience-based interoperability guidance. Informative References This specification defines HPACK, a compression format for efficiently representing HTTP header fields, to be used in HTTP/2. This specification describes how to declare in a JSON Web Token (JWT) that the presenter of the JWT possesses a particular proof-of- possession key and how the recipient can cryptographically confirm proof of possession of the key by the presenter. Being able to prove possession of a key is also sometimes described as the presenter being a holder-of-key. This document specifies version 1.3 of the Transport Layer Security (TLS) protocol. TLS allows client/server applications to communicate over the Internet in a way that is designed to prevent eavesdropping, tampering, and message forgery. This document updates RFCs 5705 and 6066, and obsoletes RFCs 5077, 5246, and 6961. This document also specifies new requirements for TLS 1.2 implementations.

Author's Address

Santa Cruz CA 95060-1950 US zenomt@zenomt.com https://zenomt.zenomt.com/card.ttl#me