Digest Headers

1.1. A Brief History of HTTP Integrity Fields

The Content-MD5 header field was originally introduced to provide integrity, but HTTP/1.1 ([RFC7231], Appendix B) obsoleted it:¶

• The Content-MD5 header field has been removed because it was inconsistently implemented with respect to partial responses.¶

[RFC3230] provided a more flexible solution introducing the concept of "instance", and the fields Digest and Want-Digest.¶

1.2. This Proposal

The concept of selected representation defined in Section 3.2 of [SEMANTICS] makes [RFC3230] definitions inconsistent with current HTTP semantics. This document updates the Digest and Want-Digest field definitions to align with [SEMANTICS] concepts.¶

Basing Digest on the selected representation makes it straightforward to apply it to use-cases where the transferred data does require some sort of manipulation to be considered a representation, or conveys a partial representation of a resource eg. Range Requests (see Section 14.2 of [SEMANTICS]).¶

This document replaces [RFC3230] to better align with [SEMANTICS] and to provide more detailed description of Digest usage in request and response cases. Changes are intended to be semantically compatible with existing implementations but note that negotiation of Content-MD5 is deprecated Section 7, Digest field parameters are obsoleted Section 8, "md5" and "sha" digest-algorithms are obsoleted Section 12.2 and the "adler32" algorithm is deprecated Section 12.3.¶

The value of Digest is calculated on selected representation, which is tied to the value contained in any Content-Encoding or Content-Type header fields. Therefore, a given resource may have multiple different digest values.¶

To allow both parties to exchange a Digest of a representation with no content codings (see Section 8.4.1 of [SEMANTICS]) two more digest-algorithms are added ("id-sha-256" and "id-sha-512").¶

1.3. Goals

The goals of this proposal are:¶

1. Digest coverage for either the resource's representation data or selected representation data communicated via HTTP.¶
2. Support for multiple digest-algorithms.¶
3. Negotiation of the use of digests.¶

The goals do not include:¶

HTTP message integrity:

Digest mechanisms do not cover the full HTTP message nor its semantic, as representation metadata is not included in the checksum.¶

HTTP field integrity:

Digest mechanisms cover only representation and selected representation data, and do not protect the integrity of associated representation metadata or other message fields.¶

Authentication:

Digest mechanisms do not support authentication of the source of a digest, message or anything else. These mechanisms, therefore, are not a sufficient defense against many kinds of malicious attacks.¶

Privacy:

Digest mechanisms do not provide message privacy.¶

Authorization:

Digest mechanisms do not support authorization or other kinds of access controls.¶

1.4. Notational Conventions

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 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶

This document uses the Augmented BNF defined in [RFC5234] and updated by [RFC7405] along with the "#rule" extension defined in Section 5.6.1 of [SEMANTICS].¶

The definitions "representation", "selected representation", "representation data", "representation metadata", and "content" in this document are to be interpreted as described in [SEMANTICS].¶

Algorithm names respect the casing used in their definition document (eg. SHA-1, CRC32c) whereas digest-algorithm tokens are quoted (eg. "sha", "crc32c").¶

6.1. Digest and PATCH

In PATCH requests, the representation digest MUST be computed on the patch document because the representation metadata refers to the patch document and not to the target resource (see Section 2 of [PATCH]).¶

In PATCH responses, the representation digest MUST be computed on the selected representation of the patched resource.¶

Digest usage with PATCH is thus very similar to POST, but with the resource's own semantic partly implied by the method and by the patch document.¶

9.1. Supporting Both SRI and Representation Digest

The SRI and Representation Digest mechanisms are different and complementary but one is not capable of replacing the other because they have different threat, security and implementation properties.¶

A user agent that supports both mechanisms is expected to apply the rules specified for each but since the two mechanisms are independent, the ordering is not important. However, a user agent supporting both could benefit from performing representation digest validation first because it does not always require a conversion into identity encoding.¶

There is a chance that a user agent supporting both mechanisms may find one validates successfully while the other fails. This document specifies no requirements or guidance for user agents that experience such cases.¶

10.1. Server Returns Full Representation Data

Request:¶

GET /items/123 HTTP/1.1
Host: foo.example

Response:¶

HTTP/1.1 200 OK
Content-Type: application/json
Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=

{"hello": "world"}

10.2. Server Returns No Representation Data

In this example, a HEAD request is used to retrieve the checksum of a resource.¶

The response Digest field-value is calculated over the JSON object {"hello": "world"}, which is not shown because there is no payload data.¶

Request:¶

HEAD /items/123 HTTP/1.1
Host: foo.example

Response:¶

HTTP/1.1 200 OK
Content-Type: application/json
Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=

10.3. Server Returns Partial Representation Data

In this example, the client makes a range request and the server responds with partial content. The Digest field-value represents the entire JSON object {"hello": "world"}.¶

Request:¶

GET /items/123 HTTP/1.1
Host: foo.example
Range: bytes=1-7

Response:¶

HTTP/1.1 206 Partial Content
Content-Type: application/json
Content-Range: bytes 1-7/18
Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=

"hello"

10.4. Client and Server Provide Full Representation Data

The request contains a Digest field-value calculated on the enclosed representation. It also includes an Accept-Encoding: br header field that advertises the client supports brotli encoding.¶

The response includes a Content-Encoding: br that indicates the selected representation is brotli encoded. The Digest field-value is therefore different compared to the request.¶

For presentation purposes, the response body is displayed as a base64-encoded string because it contains non-printable characters.¶

Request:¶

PUT /items/123 HTTP/1.1
Host: foo.example
Content-Type: application/json
Accept-Encoding: br
Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=

{"hello": "world"}

Response:¶

HTTP/1.1 200 Ok
Content-Type: application/json
Content-Location: /items/123
Content-Encoding: br
Content-Length: 22
Digest: sha-256=4REjxQ4yrqUVicfSKYNO/cF9zNj5ANbzgDZt3/h3Qxo=

iwiAeyJoZWxsbyI6ICJ3b3JsZCJ9Aw==

10.5. Client Provides Full Representation Data, Server Provides No Representation Data

The request Digest field-value is calculated on the enclosed payload.¶

The response Digest field-value depends on the representation metadata header fields, including Content-Encoding: br even when the response does not contain content.¶

Request:¶

PUT /items/123 HTTP/1.1
Host: foo.example
Content-Type: application/json
Content-Length: 18
Accept-Encoding: br
Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=

{"hello": "world"}

Response:¶

HTTP/1.1 204 No Content
Content-Type: application/json
Content-Encoding: br
Digest: sha-256=4REjxQ4yrqUVicfSKYNO/cF9zNj5ANbzgDZt3/h3Qxo=

10.6. Client and Server Provide Full Representation Data, Client Uses id-sha-256.

The response contains two digest values:¶

• one with no content coding applied, which in this case accidentally matches the unencoded digest-value sent in the request;¶
• one taking into account the Content-Encoding.¶

As the response body contains non-printable characters, it is displayed as a base64-encoded string.¶

Request:¶

PUT /items/123 HTTP/1.1
Host: foo.example
Content-Type: application/json
Accept-Encoding: br
Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=

{"hello": "world"}

Response:¶

HTTP/1.1 200 OK
Content-Type: application/json
Content-Encoding: br
Content-Location: /items/123
Digest: sha-256=4REjxQ4yrqUVicfSKYNO/cF9zNj5ANbzgDZt3/h3Qxo=,
        id-sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=

iwiAeyJoZWxsbyI6ICJ3b3JsZCJ9Aw==

10.7. POST Response does not Reference the Request URI

The request Digest field-value is computed on the enclosed representation (see Section 6).¶

The representation enclosed in the response refers to the resource identified by Content-Location (see [SEMANTICS], Section 6.4.2). Digest is thus computed on the enclosed representation.¶

Request:¶

POST /books HTTP/1.1
Host: foo.example
Content-Type: application/json
Accept: application/json
Accept-Encoding: identity
Digest: sha-256=bWopGGNiZtbVgHsG+I4knzfEJpmmmQHf7RHDXA3o1hQ=

{"title": "New Title"}

Response:¶

HTTP/1.1 201 Created
Content-Type: application/json
Content-Location: /books/123
Location: /books/123
Digest: id-sha-256=yxOAqEeoj+reqygSIsLpT0LhumrNkIds5uLKtmdLyYE=

{
  "id": "123",
  "title": "New Title"
}

Note that a 204 No Content response without content but with the same Digest field-value would have been legitimate too.¶

10.8. POST Response Describes the Request Status

The request Digest field-value is computed on the enclosed representation (see Section 6).¶

The representation enclosed in the response describes the status of the request, so Digest is computed on that enclosed representation.¶

Response Digest has no explicit relation with the resource referenced by Location.¶

Request:¶

POST /books HTTP/1.1
Host: foo.example
Content-Type: application/json
Accept: application/json
Accept-Encoding: identity
Digest: sha-256=bWopGGNiZtbVgHsG+I4knzfEJpmmmQHf7RHDXA3o1hQ=
Location: /books/123

{"title": "New Title"}

Response:¶

HTTP/1.1 201 Created
Content-Type: application/json
Digest: id-sha-256=2LBp5RKZGpsSNf8BPXlXrX4Td4Tf5R5bZ9z7kdi5VvY=
Location: /books/123

{
  "status": "created",
  "id": "123",
  "ts": 1569327729,
  "instance": "/books/123"
}

10.9. Digest with PATCH

This case is analogous to a POST request where the target resource reflects the effective request URI.¶

The PATCH request uses the application/merge-patch+json media type defined in [RFC7396].¶

Digest is calculated on the enclosed payload, which corresponds to the patch document.¶

The response Digest field-value is computed on the complete representation of the patched resource.¶

Request:¶

PATCH /books/123 HTTP/1.1
Host: foo.example
Content-Type: application/merge-patch+json
Accept: application/json
Accept-Encoding: identity
Digest: sha-256=bWopGGNiZtbVgHsG+I4knzfEJpmmmQHf7RHDXA3o1hQ=

{"title": "New Title"}

Response:¶

HTTP/1.1 200 OK
Content-Type: application/json
Digest: id-sha-256=yxOAqEeoj+reqygSIsLpT0LhumrNkIds5uLKtmdLyYE=

{
  "id": "123",
  "title": "New Title"
}

Note that a 204 No Content response without content but with the same Digest field-value would have been legitimate too.¶

10.10. Error responses

In error responses, the representation-data does not necessarily refer to the target resource. Instead, it refers to the representation of the error.¶

In the following example a client attempts to patch the resource located at /books/123. However, the resource does not exist and the server generates a 404 response with a body that describes the error in accordance with [RFC7807].¶

The response Digest field-value is computed on this enclosed representation.¶

Request:¶

PATCH /books/123 HTTP/1.1
Host: foo.example
Content-Type: application/merge-patch+json
Accept: application/json
Accept-Encoding: identity
Digest: sha-256=bWopGGNiZtbVgHsG+I4knzfEJpmmmQHf7RHDXA3o1hQ=

{"title": "New Title"}

Response:¶

HTTP/1.1 404 Not Found
Content-Type: application/problem+json
Digest: sha-256=KPqhVXAT25LLitV1w0O167unHmVQusu+fpxm65zAsvk=

{
  "title": "Not Found",
  "detail": "Cannot PATCH a non-existent resource",
  "status": 404
}

10.11. Use with Trailer Fields and Transfer Coding

An origin server sends Digest as trailer field, so it can calculate digest-value while streaming content and thus mitigate resource consumption. The Digest field-value is the same as in Section 10.1 because Digest is designed to be independent from the use of one or more transfer codings (see Section 2).¶

Request:¶

GET /items/123 HTTP/1.1
Host: foo.example

Response:¶

HTTP/1.1 200 OK
Content-Type: application/json
Transfer-Encoding: chunked
Trailer: Digest

8\r\n
{"hello"\r\n
8
: "world\r\n
2\r\n
"}\r\n
0\r\n
Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=

11.1. Server Selects Client's Least Preferred Algorithm

The client requests a digest, preferring "sha". The server is free to reply with "sha-256" anyway.¶

Request:¶

GET /items/123 HTTP/1.1
Host: foo.example
Want-Digest: sha-256;q=0.3, sha;q=1

Response:¶

HTTP/1.1 200 OK
Content-Type: application/json
Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=

{"hello": "world"}

11.2. Server Selects Algorithm Unsupported by Client

The client requests a "sha" digest only. The server is currently free to reply with a Digest containing an unsupported algorithm.¶

Request:¶

GET /items/123 HTTP/1.1
Host: foo.example
Want-Digest: sha;q=1

Response:¶

HTTP/1.1 200 OK
Content-Type: application/json
Digest: id-sha-512=WZDPaVn/7XgHaAy8pmojAkGWoRx2UFChF41A2svX+TaPm
                   +AbwAgBWnrIiYllu7BNNyealdVLvRwE\nmTHWXvJwew==

{"hello": "world"}

11.3. Server Does Not Support Client Algorithm and Returns an Error

The client requests a "sha" Digest, the server advises "sha-256" and "sha-512".¶

Request:¶

GET /items/123 HTTP/1.1
Host: foo.example
Want-Digest: sha;q=1

Response:¶

HTTP/1.1 400 Bad Request
Want-Digest: sha-256, sha-512

12.1. Digest Does Not Protect the Full HTTP Message

This document specifies a data integrity mechanism that protects HTTP representation data, but not HTTP representation metadata fields, from certain kinds of accidental corruption.¶

Digest is not intended to be a general protection against malicious tampering with HTTP messages. This can be achieved by combining it with other approaches such as transport-layer security or digital signatures.¶

12.2. Broken Cryptographic Algorithms

Cryptographic algorithms are intended to provide a proof of integrity suited towards cryptographic constructions such as signatures.¶

However, these rely on collision-resistance for their security proofs [CMU-836068]. The "md5" and "sha" digest-algorithms are vulnerable to collisions attacks, so they MUST NOT be used with Digest.¶

12.3. Other Deprecated Algorithms

The ADLER32 algorithm defined in [RFC1950] has been deprecated by [RFC3309] because, under certain conditions, it provides weak detection of errors. It is now NOT RECOMMENDED for use with Digest.¶

12.4. Digest for End-to-End Integrity

Digest only covers the representation data and not the representation metadata. Digest could help protect the representation data from buggy manipulation, undesired "transforming proxies" (see Section 7.7 of [SEMANTICS]) or other actions as the data passes across multiple hops or system boundaries. Even a simple mechanism for end-to-end representation data integrity is valuable because user-agent can validate that resource retrieval succeeded before handing off to a HTML parser, video player etc. for parsing.¶

Identity digest-algorithms (e.g. "id-sha-256" and "id-sha-512") are particularly useful for end-to-end integrity because they allow piecing together a resource from different sources with different HTTP messaging characteristics. For example, different servers that apply different content codings.¶

Note that using Digest alone does not provide end-to-end integrity of HTTP messages over multiple hops, since metadata could be manipulated at any stage. Methods to protect metadata are discussed in Section 12.6.¶

12.5. Digest and Content-Location in Responses

When a state-changing method returns the Content-Location header field, the enclosed representation refers to the resource identified by its value and Digest is computed accordingly.¶

12.6. Usage in Signatures

Digital signatures are widely used together with checksums to provide the certain identification of the origin of a message [NIST800-32]. Such signatures can protect one or more HTTP fields and there are additional considerations when Digest is included in this set.¶

Since the Digest field is a hash of a resource representation, it explicitly depends on the representation metadata (eg. the values of Content-Type, Content-Encoding etc). A signature that protects Digest but not other representation metadata can expose the communication to tampering. For example, an actor could manipulate the Content-Type field-value and cause a digest validation failure at the recipient, preventing the application from accessing the representation. Such an attack consumes the resources of both endpoints. See also Section 12.5.¶

Digest SHOULD always be used over a connection that provides integrity at the transport layer that protects HTTP fields.¶

A Digest field using NOT RECOMMENDED digest-algorithms SHOULD NOT be used in signatures.¶

Using signatures to protect the Digest of an empty representation allows receiving endpoints to detect if an eventual payload has been stripped or added.¶

Any mangling of Digest, including de-duplication of representation-data-digest values or combining different field values (see Section 5.2 of [SEMANTICS]) might affect signature validation.¶

12.7. Usage in Trailer Fields

When Digest is used in trailer fields, the receiver gets the digest value after the content and may thus be tempted to process the data before validating the digest value. It is prefereable that data is only be processed after validating the Digest.¶

If received in trailers, Digest MUST NOT be discarded; instead, it MAY be merged in the header section (See Section 6.5.1 of [SEMANTICS]).¶

Not every digest-algorithm is suitable for use in the trailer section, some may require to pre-process the whole payload before sending a message (eg. see [I-D.thomson-http-mice]).¶

12.8. Usage with Encryption

Digest may expose details of encrypted payload when the checksum is computed on the unencrypted data. For example, the use of the "id-sha-256" digest-algorithm in conjunction with the encrypted content-coding [RFC8188].¶

The representation-data-digest of an encrypted payload can change between different messages depending on the encryption algorithm used; in those cases its value could not be used to provide a proof of integrity "at rest" unless the whole (e.g. encoded) content is persisted.¶

12.9. Algorithm Agility

The security properties of digest-algorithms are not fixed. Algorithm Agility (see [RFC7696]) is achieved by providing implementations with flexibility choose digest-algorithms from the IANA Digest Algorithm Values registry in Section 13.1.¶

To help endpoints understand weaker algorithms from stronger ones, this document adds to the IANA Digest Algorithm Values registry a new "Status" field containing the most-recent appraisal of the digest-algorithm; the allowed values are specified in Section 13.2.¶

An endpoint might have a preference for algorithms, such as preferring "standard" algorithms over "deprecated" ones. Transition from weak algorithms is supported by negotiation of digest-algorithm using Want-Digest (see Section 4) or by sending multiple representation-data-digest values from which the receiver chooses. Endpoints are advised that sending multiple values consumes resources, which may be wasted if the receiver ignores them (see Section 3).¶

Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=,
        sha-256=47DEQpj8HBSa+/TImW+5JCeuQeRkm5NMpJWZG3hSuFU=

12.10. Resource exhaustion

Digest validation consumes computational resources. In order to avoid resource exhaustion, implementations can restrict validation of the algorithm types, number of validations, or the size of content.¶

13.1. Establish the HTTP Digest Algorithm Values Registry

This memo sets this specification to be the establishing document for the HTTP Digest Algorithm Values registry.¶

13.2. The "status" Field in the HTTP Digest Algorithm Values Registry

This memo adds the field "Status" to the HTTP Digest Algorithm Values registry. The allowed values for the "Status" fields are described below.¶

Status

• "standard" for standardized algorithms without known problems;¶
• "experimental", "obsoleted" or some other appropriate value - e.g. according to the type and status of the primary document in which the algorithm is defined;¶
• "deprecated" when the algorithm is insecure or otherwise undesirable.¶

13.3. Deprecate "MD5" Digest Algorithm

This memo updates the "MD5" digest-algorithm in the HTTP Digest Algorithm Values registry:¶

• Digest Algorithm: md5¶
• Description: As specified in Section 5.¶
• Status: As specified in Section 5.¶

13.4. Update "UNIXsum" Digest Algorithm

This memo updates the "UNIXsum" digest-algorithm in the HTTP Digest Algorithm Values registry:¶

• Digest Algorithm: As specified in Section 5.¶
• Description: As specified in Section 5.¶
• Status: As specified in Section 5.¶

13.5. Update "UNIXcksum" Digest Algorithm

This memo updates the "UNIXcksum" digest-algorithm in the HTTP Digest Algorithm Values registry:¶

• Digest Algorithm: As specified in Section 5.¶
• Description: As specified in Section 5.¶
• Status: As specified in Section 5.¶

13.6. Update "CRC32c" Digest Algorithm

This memo updates the "CRC32c" digest-algorithm in the HTTP Digest Algorithm Values registry:¶

• Digest Algorithm: crc32c¶
• Description: The CRC32c algorithm is a 32-bit cyclic redundancy check. It achieves a better hamming distance (for better error-detection performance) than many other 32-bit CRC functions. Other places it is used include iSCSI and SCTP. The 32-bit output is encoded in hexadecimal (using between 1 and 8 ASCII characters from 0-9, A-F, and a-f; leading 0's are allowed). For example, crc32c=0a72a4df and crc32c=A72A4DF are both valid checksums for the 3-byte message "dog".¶
• Reference: [RFC4960] appendix B, this document.¶
• Status: standard.¶

13.7. Deprecate "SHA" Digest Algorithm

This memo updates the "SHA" digest-algorithm in the HTTP Digest Algorithm Values registry:¶

• Digest Algorithm: sha¶
• Description: As specified in Section 5.¶
• Status: As specified in Section 5.¶

13.8. Obsolete "ADLER32" Digest Algorithm

This memo updates the "ADLER32" digest-algorithm in the HTTP Digest Algorithm Values registry:¶

• Digest Algorithm: adler32¶
• Description: The ADLER32 algorithm is a checksum specified in [RFC1950] "ZLIB Compressed Data Format". The 32-bit output is encoded in hexadecimal (using between 1 and 8 ASCII characters from 0-9, A-F, and a-f; leading 0's are allowed). For example, adler32=03da0195 and adler32=3DA0195 are both valid checksums for the 4-byte message "Wiki". This algorithm is obsoleted and SHOULD NOT be used.¶
• Status: obsoleted¶

13.9. Obsolete "contentMD5" token in Digest Algorithm

This memo adds the "contentMD5" token in the HTTP Digest Algorithm Values registry:¶

• Digest Algorithm: contentMD5¶
• Description: Section 5 of [RFC3230] defined the "contentMD5" token to be used only in Want-Digest. This token is obsoleted and MUST NOT be used.¶
• Reference: Section 13.9 of this document, Section 5 of [RFC3230].¶
• Status: obsoleted¶

13.10. The "id-sha-256" Digest Algorithm

This memo registers the "id-sha-256" digest-algorithm in the HTTP Digest Algorithm Values registry:¶

• Digest Algorithm: id-sha-256¶
• Description: As specified in Section 5.¶
• Status: As specified in Section 5.¶

13.11. The "id-sha-512" Digest Algorithm

This memo registers the "id-sha-512" digest-algorithm in the HTTP Digest Algorithm Values registry:¶

• Digest Algorithm: id-sha-512¶
• Description: As specified in Section 5.¶
• Status: As specified in Section 5.¶

13.12. Changes Compared to RFC5843

The digest-algorithm values for "MD5", "SHA", "SHA-256", "SHA-512", "UNIXcksum", "UNIXsum", "ADLER32" and "CRC32c" have been updated to lowercase.¶

The status of "MD5" has been updated to "deprecated", and its description states that this algorithm MUST NOT be used.¶

The status of "SHA" has been updated to "deprecated", and its description states that this algorithm MUST NOT be used.¶

The status for "CRC2c", "UNIXsum" and "UNIXcksum" has been updated to "standard".¶

The "id-sha-256" and "id-sha-512" algorithms have been added to the registry.¶

13.13. Want-Digest Field Registration

This section registers the Want-Digest field in the "Hypertext Transfer Protocol (HTTP) Field Name Registry" [SEMANTICS].¶

Field name: Want-Digest¶

Status: permanent¶

Specification document(s): Section 4 of this document¶

13.14. Digest Field Registration

This section registers the Digest field in the "Hypertext Transfer Protocol (HTTP) Field Name Registry" [SEMANTICS].¶

Field name: Digest¶

Status: permanent¶

Specification document(s): Section 3 of this document¶

Since draft-ietf-httpbis-digest-headers-04

• Improve SRI section #1354¶
• About duplicate digest-algorithms #1221¶
• Improve security considerations #852¶
• md5 and sha deprecation references #1392¶
• Obsolete 3230 #1395¶
• Editorial #1362¶

Since draft-ietf-httpbis-digest-headers-03

• Reference semantics-12¶
• Detail encryption quirks¶
• Details on Algorithm agility #1250¶
• Obsolete parameters #850¶

Since draft-ietf-httpbis-digest-headers-02

• Deprecate SHA-1 #1154¶
• Avoid id-* with encrypted content¶
• Digest is independent from MESSAGING and HTTP/1.1 is not normative #1215¶
• Identity is not a valid field value for content-encoding #1223¶
• Mention trailers #1157¶
• Reference httpbis-semantics #1156¶
• Add contentMD5 as an obsoleted digest-algorithm #1249¶
• Use lowercase digest-algorithms names in the doc and in the digest-algorithm IANA table.¶

Since draft-ietf-httpbis-digest-headers-01

• Digest of error responses is computed on the error representation-data #1004¶
• Effect of HTTP semantics on payload and message body moved to appendix #1122¶
• Editorial refactoring, moving headers sections up. #1109-#1112, #1116, #1117, #1122-#1124¶

Since draft-ietf-httpbis-digest-headers-00

• Align title with document name¶
• Add id-sha-* algorithm examples #880¶
• Reference [RFC6234] and [RFC3174] instead of FIPS-1¶
• Deprecate MD5¶
• Obsolete ADLER-32 but don't forbid it #828¶
• Update CRC32C value in IANA table #828¶
• Use when acting on resources (POST, PATCH) #853¶
• Added Relationship with SRI, draft Use Cases #868, #971¶
• Warn about the implications of Content-Location¶