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truncatedSha512Iv

Compute the IV for a truncated version of SHA512 per FIPS 180 Section 5.3.6

sha2.truncatedSha512Iv

fn truncatedSha512Iv(digest_len: comptime_int) Iv64

File

lib/std/crypto/sha2.zig:714

Code

fn truncatedSha512Iv(digest_len: comptime_int) Iv64 {
    const assert = std.debug.assert;
    comptime assert(digest_len > 1);
    comptime assert(digest_len <= 512);
    comptime assert(digest_len != 384); // NIST specially defines this (see `iv384`)

    comptime var gen_params = iv512;
    inline for (&gen_params) |*iv| {
        iv.* ^= 0xa5a5a5a5a5a5a5a5;
    }
    const GenHash = Sha2x64(gen_params, 512);

    var params: [@sizeOf(Iv64)]u8 = undefined;
    const algo_str = std.fmt.comptimePrint("SHA-512/{d}", .{digest_len});
    GenHash.hash(algo_str, &params, .{});

    return Iv64{
        std.mem.readInt(u64, params[0..8], .big),
        std.mem.readInt(u64, params[8..16], .big),
        std.mem.readInt(u64, params[16..24], .big),
        std.mem.readInt(u64, params[24..32], .big),
        std.mem.readInt(u64, params[32..40], .big),
        std.mem.readInt(u64, params[40..48], .big),
        std.mem.readInt(u64, params[48..56], .big),
        std.mem.readInt(u64, params[56..64], .big),
    };
}