HELP! - challange handshake authentication and MD5 - PPP

This is a discussion on HELP! - challange handshake authentication and MD5 - PPP ; Hello. RFC - 1321 says: ........ STEP 4 .... Do the following: /* Process each 16-word block. */ For i = 0 to N/16-1 do /* Copy block i into X. */ For j = 0 to 15 do Set ...

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Thread: HELP! - challange handshake authentication and MD5

  1. HELP! - challange handshake authentication and MD5

    Hello.

    RFC - 1321 says:
    ........
    STEP 4
    ....
    Do the following:
    /* Process each 16-word block. */
    For i = 0 to N/16-1 do

    /* Copy block i into X. */
    For j = 0 to 15 do
    Set X[j] to M[i*16+j].
    end /* of loop on j */

    In RFC nothing said about N, X[j], M[i*16+j], what is it?
    What mean these operations Set X[j] to M[i*16+j]. ?

    I dont fully understand how this "do the folowing" is doing - all functions
    is 32 bit, what do they mean each *16-word* block? How its processed?

    PS:
    What is it for? chap? Everybody knows md5, and on all requests will be
    given right "message digest". CHAP is usefulless, PAP is more useful.




  2. Re: HELP! - challange handshake authentication and MD5

    "Andrey A. Pospelov" writes:
    > In RFC nothing said about N, X[j], M[i*16+j], what is it?


    It's all defined in the text above that pseudo-code -- N is the number
    of bits in the message. X[j] is the j'th bit of word X.

    > What mean these operations Set X[j] to M[i*16+j]. ?


    It means to copy the bit from M[i*16+j] to X[j].

    The C source code in appendix A might be easier to work with.

    > What is it for? chap? Everybody knows md5, and on all requests will be
    > given right "message digest". CHAP is usefulless, PAP is more useful.


    I don't know what you're saying there.

    PPP's CHAP mechanism uses a shared secret to validate the peers.
    PPP's PAP requires that the secret be sent over the wire -- but CHAP
    does not.

    --
    James Carlson, IP Systems Group
    Sun Microsystems / 1 Network Drive 71.234W Vox +1 781 442 2084
    MS UBUR02-212 / Burlington MA 01803-2757 42.497N Fax +1 781 442 1677

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