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Asked: 2026-05-26T09:13:26+00:00

EDIT: Sorry I forgot to mention, I’m not using the implemented sha512 crypt because

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EDIT: Sorry I forgot to mention, I’m not using the implemented sha512 crypt because as far as I can tell it doesn’t involve a salt value or a specified number of rounds to compute the hash with.

Okay so I’m coding the sha-512 crypt in c# and I’m following the steps found here…

http://people.redhat.com/drepper/SHA-crypt.txt

This is my first time doing anything encryption related so I want to make sure I’m understanding the steps correctly… I don’t understand c code well enough to direct translation from c to c# :/

I have assumed finishing a digest is the same as computing the hash. In this case, I’ve also assumed that when the steps refer to a finished digest, they are referring the the computed hash, rather than the pre-hash computed digest bytes. Correct me if I’m wrong please!

Assuming everything has been done correctly for steps 1-8, my doubts start at step 9

9. For each block of 32 or 64 bytes in the password string (excluding
the terminating NUL in the C representation), add digest B to digest A

Since I’m using SHA-512, I have block sizes of 64 bytes.

Would the following code produce the desired result?

//FYI, temp = digestA from steps 1-3 (before expanding digestA for step 9)
//alt_result = computed digestB hash (64 byte hash)

for (cnt = key.Length; cnt > 64; cnt -= 64)                         //9
{
    int i = 0;
    ctx.TransformBlock(alt_result, 0, 64, digestA, temp.Length + 64 * i);
    i++;
}

If anyone can clarify that what I’ve stated is correct, I would appreciate it. Thanks!

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1 Answer

  1. Editorial Team

    Salting is as simple as appending a fixed byte string on the end of your input string. Essentially providing a known “homegrown” transform to your input.

    About the algorithm itself: you seem to be starting at a disadvantage. A neophyte, you’re making a lot of “assumptions” about basic crypting terminology that even need clarification. If the CLR implementation won’t work for you, I think your time would be better spent finding a good C implementation and figuring out how to integrate to that. Figuring out the interop (extern) calls to that will be far easier than diving into the intracacies of crypting, the results will be more efficient, and the knowledge you gain about native interop will be far more useful/reusable.

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