peass-ng/PEASS-ng · error · ArgumentException

needs to be a multiple of 8

Error message

needs to be a multiple of 8

What it means

Sha512tDigest truncates SHA-512 to bitLength bits, and truncation is only well-defined on byte boundaries, so the constructor requires bitLength % 8 == 0. The library throws ArgumentException('needs to be a multiple of 8') otherwise.

Source

Thrown at winPEAS/winPEASexe/winPEAS/3rdParty/BouncyCastle/crypto/digests/Sha512tDigest.cs:26

     */
    public class Sha512tDigest
        : LongDigest
    {
        private const ulong A5 = 0xa5a5a5a5a5a5a5a5UL;

        private readonly int digestLength;

        private ulong H1t, H2t, H3t, H4t, H5t, H6t, H7t, H8t;

        /**
         * Standard constructor
         */
        public Sha512tDigest(int bitLength)
        {
            if (bitLength >= 512)
                throw new ArgumentException("cannot be >= 512", "bitLength");
            if (bitLength % 8 != 0)
                throw new ArgumentException("needs to be a multiple of 8", "bitLength");
            if (bitLength == 384)
                throw new ArgumentException("cannot be 384 use SHA384 instead", "bitLength");

            this.digestLength = bitLength / 8;

            tIvGenerate(digestLength * 8);

            Reset();
        }

        /**
         * Copy constructor.  This will copy the state of the provided
         * message digest.
         */
        public Sha512tDigest(Sha512tDigest t)
            : base(t)
        {
            this.digestLength = t.digestLength;

View on GitHub (pinned to 53fb989abc)

Solutions

1. Pass a bitLength that is a multiple of 8 (e.g. 8, 16, ..., 504) and also < 512 and != 384.
2. If you have a byte length, multiply by 8 before passing it.
3. Validate input before constructing if the value comes from external config.

Example fix

// before
var digest = new Sha512tDigest(254);
// after
var digest = new Sha512tDigest(256);

if (bitLength % 8 != 0 || bitLength >= 512 || bitLength == 384) throw new ArgumentOutOfRangeException(nameof(bitLength));

bool IsByteAligned(int bits) => bits % 8 == 0;

try { var d = new Sha512tDigest(bits); }
catch (ArgumentException ex) when (ex.ParamName == "bitLength") { bits = (bits / 8 + 1) * 8; d = new Sha512tDigest(bits); }

When it happens

Trigger: new Sha512tDigest(bitLength) with a bitLength not divisible by 8, e.g. 253 or 511.

Common situations: Parsing a bit size from a string like 'SHA-512/254' or computing bitLength from bytes incorrectly (multiplying by 4 instead of 8).

Related errors

• cannot be >= 512
• cannot be 384 use SHA384 instead
• baseDigest output not large enough to support length
• BLAKE2b digest bit length must be a multiple of 8 and not gr
• Invalid digest length (required: 1 - 64)

AI-assisted analysis of peass-ng/PEASS-ng@53fb989abc (2026-09-02). Data as JSON: /api/errors/8c115e7fda497912. Report an issue: GitHub.