Tagged Questions

Fixed, more or less arbitrary parameter values that appear in the definitions of cryptographic schemes, such as fixed initialization vectors for hash functions or S-box tables for block ciphers.

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7
votes
1answer
177 views

How many degrees of freedom up my sleeve?

Now that we know how the MD2 S-box was constructed, I find myself wondering how good a nothing up my sleeve number it really is. It is derived from $\pi$, but not in a very obvious way, even in ...
5
votes
1answer
174 views

Significance of rotation constants in SHA-512?

In a single round of SHA-512, in the operations $\Sigma_0(A)$, $\Sigma_1(E)$ why are the constants $28$, $34$, and $39$ used for the number of rotations? What significance do these numbers have? What ...
2
votes
1answer
190 views

Are the MD5 constants an S-Box?

I noticed that several hash algorithms, in this case MD5, defines some constants. MD5 defines 64 constant values (the shift count per round) which also gets expand (via sine) to a summand for a ...
28
votes
1answer
1k views

How is the MD2 hash function S-table constructed from Pi?

For fun, I'm learning more about cryptography and hashing. I'm implementing the MD2 hash function following RFC 1319 (http://tools.ietf.org/html/rfc1319). I'll preface by saying I know there are ...
7
votes
1answer
373 views

Why are the initial states of hashes functions (like SHA-1) often non-zero?

There is already a question asking "Why initialize SHA1 with specific buffer?" and my question follows on from this: Why are the initial states of hash functions often non-zero? For most, I have ...