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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

6.1.3. Encryption Scheme

RSA Optimal Asymmetric Encryption Padding (RSAES-OAEP) [PKCS#1], using hash function SHA-1, mask generation function MGF1 (with SHA-1), and the empty-string for the "label" parameter.

Note: whereas SHA-256 is specified as the Hash Algorithm primitive for employment elsewhere in the protocol, the choice of the SHA-1 here is made for the following reasons:

The potential cryptanalytic vulnerability of SHA-1 is not relevant in this context. The role of the hash algorithm in OAEP is merely to hash the label parameter which in this instance is a known constant.
OAEP with SHA-1 is widely implemented.