• b1 = MD5(S + RA)____|____ c(1) = p1 xor b1
  • b2 = MD5(S + c(1))____|____ c(2) = p2 xor b2
  • . .
  • . .
  • . .
  • bi = MD5(S + c(i-1))____|____ c(i) = pi xor bi

this is the encryption algorithm used by the radius protocol.

Basically p is the password, that gets broken down to blocks of 16 bits, p1,p2,p3... (if its not a multiple of 16 the last block gets padded with nulls. S is the shared secret and RA is an authenticator pseudo-random value (both are known constants). + denotes concatenation of strings

If I have RA, S and c how to I reverse this to get p?

PS: sorry for horrible formatting, this is how the show it in the rfc and I had no idea how to format it better

  • 2
    If there is an RFC for the algorithm why don't you name the algorithm and provide a link to the RFC? – Robert Mar 28 '20 at 16:20

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