gchq/CyberChef · error · OperationError

Unknown padding type: ${padding}

Error message

Unknown padding type: ${padding}

What it means

Thrown by RC6.applyPadding when the `padding` argument matches none of the handled cases ('NO','PKCS5','ZERO','RANDOM','BIT'). Indicates a typo, an unsupported scheme, or an undefined value.

Source

Thrown at src/core/lib/RC6.mjs:386

                paddedMessage.push(0);
            }
            break;

        case "RANDOM":
            for (let i = 0; i < nPadding; i++) {
                paddedMessage.push(Math.floor(Math.random() * 256));
            }
            break;

        case "BIT":
            paddedMessage.push(0x80);
            for (let i = 1; i < nPadding; i++) {
                paddedMessage.push(0);
            }
            break;

        default:
            throw new OperationError(`Unknown padding type: ${padding}`);
    }

    return paddedMessage;
}

/**
 * Remove padding from message
 * @param {number[]} message - Padded message
 * @param {string} padding - Padding type ("NO", "PKCS5", "ZERO", "RANDOM", "BIT")
 * @param {number} blockSize - Block size in bytes
 * @returns {number[]} - Unpadded message
 */
function removePadding(message, padding, blockSize) {
    if (message.length === 0) return message;

    switch (padding) {
        case "NO":
        case "ZERO":

View on GitHub (pinned to 4290ea7539)

Solutions

1. Use one of the supported values exactly: 'NO','PKCS5','ZERO','RANDOM','BIT'.
2. If you need PKCS7, note that for RC6's 16-byte block PKCS5 and PKCS7 are equivalent — use 'PKCS5'.
3. Validate the padding value against the allowed list before calling.

Example fix

// before
encryptRC6(msg, key, iv, 'CBC', 'PKCS7');
// after
encryptRC6(msg, key, iv, 'CBC', 'PKCS5');

const RC6_PADDINGS = new Set(['NO','PKCS5','ZERO','RANDOM','BIT']);
if (!RC6_PADDINGS.has(padding)) {
  throw new Error(`Unknown RC6 padding '${padding}'`);
}

function isRc6Padding(p) {
  return ['NO','PKCS5','ZERO','RANDOM','BIT'].includes(p);
}

try {
  return encryptRC6(message, key, iv, mode, padding, rounds, w);
} catch (e) {
  if (e instanceof OperationError && /Unknown padding type/.test(e.message)) {
    return encryptRC6(message, key, iv, mode, 'PKCS5', rounds, w);
  }
  throw e;
}

When it happens

Trigger: Calling encryptRC6/decryptRC6 with a padding string outside the supported set, e.g. 'PKCS7', 'ISO10126', 'ANSIX923', '', or undefined (the default parameter is 'PKCS5' but an explicit undefined passed positionally overrides nothing — explicit bad strings do hit it).

Common situations: Confusing PKCS5 with PKCS7; passing a padding name from a different library; UI dropdown value renamed; forgotten argument shifting positions.

Related errors

• No padding requested but input is not a ${blockSize}-byte mu
• Invalid PKCS#5 padding.
• Invalid BIT padding.
• Letter ${letter} is not included in LS47
• No padding requested but input is not a ${blockSize}-byte mu

AI-assisted analysis of gchq/CyberChef@4290ea7539 (2026-08-13). Data as JSON: /api/errors/091d0bddc03324a2. Report an issue: GitHub.