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ShimSham

ShimSham is a Nim module to encompass several different digest/hashing algorithms. So far included are

• JH
• SHA-2
• SHA-3
• SipHash
• Tiger
• Whirlpool

There will be more soon, as well as a common hashing interface.

Using the Tiger hash as an example, here's how you get hashes:

import shimsham/tiger

echo tiger("") # gives "24f0130c63ac933216166e76b1bb925ff373de2d49584e7a"
echo tiger("abc") # gives "f258c1e88414ab2a527ab541ffc5b8bf935f7b951c132951"

The other hashes work in the same way. The whirlpool module provides the whirlpool function. The sha512 module provides sha512 and sha384. The sha256 module provides sha256 and sha224.

You can get more fine-tuned control with the following type of code:

import shimsham/sha256

var message = "My message to hash"
var m = initSha256(message) # initializes a `Sha256` object with `message`
echo m # gives "aefd1872a4eb24a79a1e727aa8c41ebde794451c0ca89a0e3abe82e45a477afc"

You can also use initSha224 if that's what you want.

initSha384 and initSha512 are available in the sha512 module.

initWhirlpool works in the same way.

Unfortunately, the Tiger module doesn't support this yet (it also has some various weird problems, which you'll see if you walk through the code).

SipHash

SipHash works a little differently. It always outputs a hash that Nim treats as a uint64. It uses two uint64 keys for input. You can do this directly using initSipState(k0,k1) where k0 and k1 are your uint64s, or you can input a long hex string directly (like initSipState("A8FC63780FB3BA3CA39580EEC5CB43B1")). After you have your state, you can update your message in various ways using input(). If you want to use a hex string for your message, too, you can do that.

Really, though, for SipHash, the easiest thing to do is to use the convenience functions siphash* where the * represents 24 or 48 for SipHash-2-4 and SipHash-4-8 (slower but more secure). Or you can specify your own SipHash-c-d values with siphash.

All you need to do then is something like:

echo siphash24("A8FC63780FB3BA3CA39580EEC5CB43B1","6018B63E6DBF9B") # gives "701bdf2ea1c82585"

JH

JH is the first SHA-3 finalist to be included here. It is usable by import-ing shimsham/jh_simple. ("Simple" is a reference to the fact that there could be some assembly support added in the future.)

Skein

Skein is the second SHA-3 finalist to be added to ShimSham. It is also much more complex than most other modules. I haven't yet had time to document all parameters, but this is based off the wonderful Skein3Fish, so you can learn more there. The simple function is skein(), which takes in different options. For example, to compute a Skein-256, with a hash length of 256, of an empty message, you can do:

import shimsham/skein

echo skein(256, 256, []) # @[0xc8,0x87,0x70,0x87,0xda,0x56,0xe0,0x72,
                         #   0x87,0x0d,0xaa,0x84,0x3f,0x17,0x6e,0x94,
                         #   0x53,0x11,0x59,0x29,0x09,0x4c,0x3a,0x40,
                         #   0xc4,0x63,0xa1,0x96,0xc2,0x9b,0xf7,0xba]

Since Skein is based off ThreeFish, you get Threefish as a bonus. It's located inside the skein directory, but it's not really intended to be part of ShimSham. Nevertheless, if you want, it's there.