gchq/CyberChef · error · OperationError

No "r" value in the signature JSON

Error message

No "r" value in the signature JSON

What it means

Thrown in ECDSAVerify.run, Raw JSON branch, when the parsed signature JSON has no truthy r field. Identical to the corresponding guard in ECDSASignatureConversion: after format resolution to Raw JSON and JSON.parse, the r scalar is checked first; a missing r aborts before s is inspected.

Source

Thrown at src/core/operations/ECDSAVerify.mjs:133

        // convert to ASN.1 signature
        let signatureASN1Hex;
        switch (inputFormat) {
            case "Auto":
                throw new OperationError("Signature format could not be detected");
            case "ASN.1 HEX":
                signatureASN1Hex = input;
                break;
            case "P1363 HEX":
                signatureASN1Hex = r.KJUR.crypto.ECDSA.concatSigToASN1Sig(input);
                break;
            case "JSON Web Signature":
                if (!inputBase64) inputBase64 = fromBase64(input, "A-Za-z0-9-_");
                signatureASN1Hex = r.KJUR.crypto.ECDSA.concatSigToASN1Sig(toHexFast(inputBase64));
                break;
            case "Raw JSON": {
                if (!inputJson) inputJson = JSON.parse(input);
                if (!inputJson.r) {
                    throw new OperationError('No "r" value in the signature JSON');
                }
                if (!inputJson.s) {
                    throw new OperationError('No "s" value in the signature JSON');
                }
                signatureASN1Hex = r.KJUR.crypto.ECDSA.hexRSSigToASN1Sig(inputJson.r, inputJson.s);
                break;
            }
        }

        // verify signature
        const internalAlgorithmName = mdAlgo.replace("-", "") + "withECDSA";
        const sig = new r.KJUR.crypto.Signature({ alg: internalAlgorithmName });
        const key = r.KEYUTIL.getKey(keyPem);
        if (key.type !== "EC") {
            throw new OperationError("Provided key is not an EC key.");
        }
        if (!key.isPublic) {
            throw new OperationError("Provided key is not a public key.");

View on GitHub (pinned to 4290ea7539)

Solutions

1. Provide JSON with lowercase 'r' and 's' hex strings.
2. Rename mismatched fields from your source data.
3. If the data is base64/concatenation, use the JSON Web Signature or P1363 format instead.

Example fix

// before
verifyRun('{"s":"a3..."}', ['Raw JSON', ...]);  // missing r
// after
verifyRun('{"r":"bb...","s":"a3..."}', ['Raw JSON', ...]);

const o = JSON.parse(sig);
if (!o || typeof o !== "object" || !o.r) throw new Error("signature JSON needs an 'r' field");

const hasR = (o) => o != null && typeof o === "object" && Object.prototype.hasOwnProperty.call(o, "r");

When it happens

Trigger: Input Format is Raw JSON (or Auto resolved there) and the object lacks 'r' - e.g. {"s":"..."}, wrong-cased keys, or unrelated JSON.

Common situations: Field-name mismatch from the producing library; truncated JSON; pasting a non-ECDSA JSON structure.

Related errors

• No "r" value in the signature JSON
• No "s" value in the signature JSON
• No "s" value in the signature JSON
• Signature format could not be detected
• Signature format could not be detected

AI-assisted analysis of gchq/CyberChef@4290ea7539 (2026-08-13). Data as JSON: /api/errors/2060a2e6fe372e73. Report an issue: GitHub.