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HTTPsec Authentication Protocol

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Preamble

1. Introduction

1.1. Editorial Conventions

1.2. Terms

1.3. Identifiers

2. Summary

2.1. Authentication Model

2.2. Peer Identifiers

2.3. Protocol Operation

2.3.1. Initialization

2.3.2. Continuation

3. Protocol Messages

3.1. Initialization Messages

3.1.1. Initialization Request

3.1.2. Initialization Response

3.2. Continuation Messages

3.2.1. Continuation Request

3.2.2. Continuation Response

3.3. Challenge Messages

3.3.1. Challenge Response

3.4. Message Flow

4. Protocol Directives

4.1. id

4.2. dh

4.3. certificate

4.4. url

4.5. group

4.6. nonce

4.7. auth

4.8. token

4.9. signature

4.10. count

4.11. mac

4.12. digest

5. Other Headers

5.1. Content-Encoding

5.2. Cache-Control

5.3. Expires

6. Protocol Computations

6.1. Algorithms

6.1.1. Hash Algorithm

6.1.2. Public Key Algorithm

6.1.3. Encryption Scheme

6.1.4. Signature Scheme

6.1.5. Block Cipher

6.1.6. Block Cipher Mode

6.2. Header Canonicalization

6.3. Initialization Transcript

6.4. Continuation Request Transcript

6.5. Continuation Response Transcript

6.6. Shared Secret

6.7. Keys

6.7.1. MAC Keys

6.7.2. Cipher Keys

6.8. Message Body Ciphering

7. Message Validation

7.1. Initialization Request Validation

7.2. Initialization Response Validation

7.3. Continuation Request Validation

7.4. Continuation Response Validation

8. Cache Considerations

9. Security Considerations

10. References

11. Editor Address

3.1.2. Initialization Response

The WWW-Authenticate header [HTTP][ 14.47] in protocol initialization responses has the following form:

"WWW-Authenticate: httpsec/1.0 initialize, "
 1#(  id
   |  dh
   | [certificate]
   |  token
   |  auth
   |  signature )
     
token       = "token=" <string-no-whitespace>
id          = "id=" <URI>
dh          = "dh=" base64
certificate = "certificate=" <URI>
auth        = "auth=" base64
signature   = "signature=" base64

Example message:

HTTP/1.1 401 Authorization Required
Expires: Thu, 11 Aug 2005 18:20:42 GMT
Cache-Control: no-transform
WWW-Authenticate: httpsec/1.0 initialize
    id=alice.example.com
    dh=+NcclW9y2I3W9X5Vy+5v5lAy4X56y+Ncrwrtv5lqe...
    certificate=http://alice.example.com/my-cert
    token=mCa5tx1vKBY
    auth=vpCNmx7MZ7iqgkzIe0HWwfyrOMeqwg0TdbpwefI...
    signature=2pX3SNgzWkV3w0W9y2X5V23hhy+5b8DQmo...

(For legibility, the example's protocol header is extended over multiple lines, as per [HTTP][4.2]. Additionally, the values of some directives are lengthy and have therefore been abbreviated; their terminating ellipsis "..." would NOT appear in the actual value.)