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Add Secp256k1Signature.isLowS

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This commit is contained in:
Simon Warta 2023-02-14 15:13:44 +01:00
parent 1ac8e429bc
commit 21e02adad4
2 changed files with 52 additions and 0 deletions
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42
packages/crypto/src/secp256k1signature.spec.ts
View File

@ -76,6 +76,48 @@ describe("Secp256k1Signature", () => {
).toThrowError(/unsigned integer s must be encoded as unpadded big endian./i); ).toThrowError(/unsigned integer s must be encoded as unpadded big endian./i);
}); });
describe("isLowS", () => {
it("works", () => {
// Signature 3045022100f25b86e1d8a11d72475b3ed273b0781c7d7f6f9e1dae0dd5d3ee9b84f3fab891022063d9c4e1391de077244583e9a6e3d8e8e1f236a3bf5963735353b93b1a3ba935
// decoded by http://asn1-playground.oss.com/
const signature = new Secp256k1Signature(
fromHex("F25B86E1D8A11D72475B3ED273B0781C7D7F6F9E1DAE0DD5D3EE9B84F3FAB891"),
fromHex("63D9C4E1391DE077244583E9A6E3D8E8E1F236A3BF5963735353B93B1A3BA935"),
);
expect(signature.isLowS()).toEqual(true);
const sig1 = Secp256k1Signature.fromDer(
fromHex(
"30440220207082eb2c3dfa0b454e0906051270ba4074ac93760ba9e7110cd94714751111022051eb0dbbc9920e72146fb564f99d039802bf6ef2561446eb126ef364d21ee9c4",
),
);
expect(sig1.isLowS()).toEqual(true);
const sig2 = Secp256k1Signature.fromDer(
fromHex(
"30440220626d61b7be1488b563e8a85bfb623b2331903964b5c0476c9f9ad29144f076fe02202002a2c0ab5e48626bf761cf677dfeede9c7309d2436d4b8c2b89f21ee2ebc6a",
),
);
expect(sig2.isLowS()).toEqual(true);
const sig3 = Secp256k1Signature.fromDer(
fromHex(
"304602210083de9be443bcf480892b8c8ca1d5ee65c79a315642c3f7b5305aff3065fda2780221009747932122b93cec42cad8ee4630a8f6cbe127578b8c495b4ab927275f657658",
),
);
expect(sig3.isLowS()).toEqual(false);
// Test data from https://github.com/randombit/botan/blob/2.9.0/src/tests/data/pubkey/ecdsa_key_recovery.vec
// This is a high-s value (`0x81F1A4457589F30D76AB9F89E748A68C8A94C30FE0BAC8FB5C0B54EA70BF6D2F > 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0` is true)
const sig4 = Secp256k1Signature.fromFixedLength(
fromHex(
"E30F2E6A0F705F4FB5F8501BA79C7C0D3FAC847F1AD70B873E9797B17B89B39081F1A4457589F30D76AB9F89E748A68C8A94C30FE0BAC8FB5C0B54EA70BF6D2F",
),
);
expect(sig4.isLowS()).toEqual(false);
});
});
it("can be encoded as fixed length", () => { it("can be encoded as fixed length", () => {
const signature = new Secp256k1Signature(new Uint8Array([0x22, 0x33]), new Uint8Array([0xaa])); const signature = new Secp256k1Signature(new Uint8Array([0x22, 0x33]), new Uint8Array([0xaa]));
expect(signature.toFixedLength()).toEqual( expect(signature.toFixedLength()).toEqual(

10
packages/crypto/src/secp256k1signature.ts
View File

@ -1,3 +1,5 @@
import BN from "bn.js";
function trimLeadingNullBytes(inData: Uint8Array): Uint8Array { function trimLeadingNullBytes(inData: Uint8Array): Uint8Array {
let numberOfLeadingNullBytes = 0; let numberOfLeadingNullBytes = 0;
for (const byte of inData) { for (const byte of inData) {
@ -12,6 +14,9 @@ function trimLeadingNullBytes(inData: Uint8Array): Uint8Array {
const derTagInteger = 0x02; const derTagInteger = 0x02;
// See https://github.com/bitcoin-core/secp256k1/blob/d644dda5c9dbdecee52d1aa259235510fdc2d4ee/include/secp256k1.h#L499-L501
const maxLowS = new BN("7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0", "hex");
export class Secp256k1Signature { export class Secp256k1Signature {
/** /**
* Takes the pair of integers (r, s) as 2x32 byte of binary data. * Takes the pair of integers (r, s) as 2x32 byte of binary data.
@ -119,6 +124,11 @@ export class Secp256k1Signature {
} }
} }
public isLowS(): boolean {
const s = new BN(this.data.s, "be");
return s.lte(maxLowS);
}
public toFixedLength(): Uint8Array { public toFixedLength(): Uint8Array {
return new Uint8Array([...this.r(32), ...this.s(32)]); return new Uint8Array([...this.r(32), ...this.s(32)]);
} }