encode

Encode a length according to NIST SP 800-185.

Function parameters

Parameters

encoding:NistLengthEncoding
len:usize

The NIST SP 800-185 encoded length format.

Types

NistLengthEncoding: The NIST SP 800-185 encoded length format.

TurboSHAKE128 is a XOF (a secure hash function with a variable output length), with a 128 bit security level.

Functions

TurboShake128: TurboSHAKE128 is a XOF (a secure hash function with a variable output length), with a 128 bit security level.
TurboShake256: TurboSHAKE256 is a XOF (a secure hash function with a variable output length), with a 256 bit security level.
Keccak: A generic Keccak hash function.
Shake: The SHAKE extendable output hash function.
TurboShake: The TurboSHAKE extendable output hash function.
CShake: The cSHAKE extendable output hash function.
KMac: The KMAC extendable output authentication function.
TupleHash: The TupleHash extendable output hash function, with domain-separated inputs.

Source

Implementation

pub fn encode(comptime encoding: NistLengthEncoding, len: usize) Length {
    const len_bits = @bitSizeOf(@TypeOf(len)) - @clz(len) + 3;
    const len_bytes = std.math.divCeil(usize, len_bits, 8) catch unreachable;

    var res = Length{ .len = len_bytes + 1 };
    if (encoding == .right) {
        res.buf[len_bytes] = @intCast(len_bytes);
    }
    const end = if (encoding == .right) len_bytes - 1 else len_bytes;
    res.buf[end] = @truncate(len << 3);
    var len_ = len >> 5;
    for (1..len_bytes) |i| {
        res.buf[end - i] = @truncate(len_);
        len_ >>= 8;
    }
    if (encoding == .left) {
        res.buf[0] = @intCast(len_bytes);
    }
    return res;
}