[Sip] questions regarding AKAv2 implementation

Ranjith.V@aricent.com Tue, 08 January 2008 10:06 UTC

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Subject: [Sip] questions regarding AKAv2 implementation
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Hi All,
        We have a question regarding the PRF function in AKAv2(IETF RFC 
4169). section 2.1 of the RFC 4169 states the following..

2.1. Password Generation

The client shall use base64 encoded [1] parameters PRF(RES||IK||CK,
"http-digest-akav2-password") as a "password" when calculating the
HTTP Digest response directive for AKAv2.

if the algorithm is AKAv2-MD5, then the PRF is HMAC_MD5.

RFC 2104 defines the HMAC_MD5 to be the following

** Function: hmac_md5
hmac_md5(text, text_len, key, key_len, digest)
unsigned char* text; /* pointer to data stream */
int text_len; /* length of data stream */
unsigned char* key; /* pointer to authentication key */
int key_len; /* length of authentication key */
caddr_t digest; /* caller digest to be filled in */

Our query
hmac_md5() function takes text , key as inputs. As we understand key 
corresponds to RES||IK||CK and text corresponds to 
"http-digest-akav2-password"...we would like to know whether our 
understanding is correct.


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