feat: add support for key type k256 (#1722)

Signed-off-by: Sai Ranjit Tummalapalli <[email protected]>

packages/askar/src/utils/askarKeyTypes.ts

@@ -29,7 +29,11 @@ const keyTypeToAskarAlg = {
   },
   [KeyType.P256]: {
     keyAlg: KeyAlgs.EcSecp256r1,
-    purposes: [AskarKeyTypePurpose.KeyManagement],
+    purposes: [AskarKeyTypePurpose.KeyManagement, AskarKeyTypePurpose.Signing],
+  },
+  [KeyType.K256]: {
+    keyAlg: KeyAlgs.EcSecp256k1,
+    purposes: [AskarKeyTypePurpose.KeyManagement, AskarKeyTypePurpose.Signing],
   },
 }
 

packages/askar/src/wallet/__tests__/AskarWallet.test.ts

@@ -59,6 +59,7 @@ describe('AskarWallet basic operations', () => {
       KeyType.Bls12381g2,
       KeyType.Bls12381g1g2,
       KeyType.P256,
+      KeyType.K256,
     ])
   })
 

packages/core/src/crypto/KeyType.ts

@@ -7,4 +7,5 @@ export enum KeyType {
   P256 = 'p256',
   P384 = 'p384',
   P521 = 'p521',
+  K256 = 'k256',
 }

packages/core/src/crypto/jose/jwa/alg.ts

@@ -12,6 +12,7 @@ export enum JwaSignatureAlgorithm {
   PS384 = 'PS384',
   PS512 = 'PS512',
   EdDSA = 'EdDSA',
+  ES256K = 'ES256K',
   None = 'none',
 }
 

packages/core/src/crypto/jose/jwa/crv.ts

@@ -4,4 +4,5 @@ export enum JwaCurve {
   P521 = 'P-521',
   Ed25519 = 'Ed25519',
   X25519 = 'X25519',
+  Secp256k1 = 'secp256k1',
 }

packages/core/src/crypto/jose/jwk/K256Jwk.ts

@@ -0,0 +1,112 @@
+import type { JwkJson } from './Jwk'
+import type { JwaEncryptionAlgorithm } from '../jwa/alg'
+
+import { TypedArrayEncoder, Buffer } from '../../../utils'
+import { KeyType } from '../../KeyType'
+import { JwaCurve, JwaKeyType } from '../jwa'
+import { JwaSignatureAlgorithm } from '../jwa/alg'
+
+import { Jwk } from './Jwk'
+import { compress, expand } from './ecCompression'
+import { hasKty, hasCrv, hasX, hasY, hasValidUse } from './validate'
+
+export class K256Jwk extends Jwk {
+  public static readonly supportedEncryptionAlgorithms: JwaEncryptionAlgorithm[] = []
+  public static readonly supportedSignatureAlgorithms: JwaSignatureAlgorithm[] = [JwaSignatureAlgorithm.ES256K]
+  public static readonly keyType = KeyType.K256
+
+  public readonly x: string
+  public readonly y: string
+
+  public constructor({ x, y }: { x: string; y: string }) {
+    super()
+
+    this.x = x
+    this.y = y
+  }
+
+  public get kty() {
+    return JwaKeyType.EC as const
+  }
+
+  public get crv() {
+    return JwaCurve.Secp256k1 as const
+  }
+
+  /**
+   * Returns the public key of the K-256 JWK.
+   *
+   * NOTE: this is the compressed variant. We still need to add support for the
+   * uncompressed variant.
+   */
+  public get publicKey() {
+    const publicKeyBuffer = Buffer.concat([TypedArrayEncoder.fromBase64(this.x), TypedArrayEncoder.fromBase64(this.y)])
+    const compressedPublicKey = compress(publicKeyBuffer)
+
+    return Buffer.from(compressedPublicKey)
+  }
+
+  public get keyType() {
+    return K256Jwk.keyType
+  }
+
+  public get supportedEncryptionAlgorithms() {
+    return K256Jwk.supportedEncryptionAlgorithms
+  }
+
+  public get supportedSignatureAlgorithms() {
+    return K256Jwk.supportedSignatureAlgorithms
+  }
+
+  public toJson() {
+    return {
+      ...super.toJson(),
+      crv: this.crv,
+      x: this.x,
+      y: this.y,
+    } as K256JwkJson
+  }
+
+  public static fromJson(jwkJson: JwkJson) {
+    if (!isValidP256JwkPublicKey(jwkJson)) {
+      throw new Error("Invalid 'K-256' JWK.")
+    }
+
+    return new K256Jwk({
+      x: jwkJson.x,
+      y: jwkJson.y,
+    })
+  }
+
+  public static fromPublicKey(publicKey: Buffer) {
+    const expanded = expand(publicKey, JwaCurve.Secp256k1)
+    const x = expanded.slice(0, expanded.length / 2)
+    const y = expanded.slice(expanded.length / 2)
+
+    return new K256Jwk({
+      x: TypedArrayEncoder.toBase64URL(x),
+      y: TypedArrayEncoder.toBase64URL(y),
+    })
+  }
+}
+
+export interface K256JwkJson extends JwkJson {
+  kty: JwaKeyType.EC
+  crv: JwaCurve.Secp256k1
+  x: string
+  y: string
+  use?: 'sig' | 'enc'
+}
+
+export function isValidP256JwkPublicKey(jwk: JwkJson): jwk is K256JwkJson {
+  return (
+    hasKty(jwk, JwaKeyType.EC) &&
+    hasCrv(jwk, JwaCurve.Secp256k1) &&
+    hasX(jwk) &&
+    hasY(jwk) &&
+    hasValidUse(jwk, {
+      supportsEncrypting: true,
+      supportsSigning: true,
+    })
+  )
+}

packages/core/src/crypto/jose/jwk/ecCompression.ts

@@ -6,14 +6,16 @@
 import bigInt from 'big-integer'
 
 import { Buffer } from '../../../utils/buffer'
+import { JwaCurve } from '../jwa'
 
 const curveToPointLength = {
-  'P-256': 64,
-  'P-384': 96,
-  'P-521': 132,
+  [JwaCurve.P256]: 64,
+  [JwaCurve.P384]: 96,
+  [JwaCurve.P521]: 132,
+  [JwaCurve.Secp256k1]: 64,
 }
 
-function getConstantsForCurve(curve: 'P-256' | 'P-384' | 'P-521') {
+function getConstantsForCurve(curve: 'P-256' | 'P-384' | 'P-521' | 'secp256k1') {
   let two, prime, b, pIdent
 
   if (curve === 'P-256') {
@@ -43,6 +45,24 @@ function getConstantsForCurve(curve: 'P-256' | 'P-384' | 'P-521') {
     pIdent = prime.add(1).divide(4)
   }
 
+  // https://en.bitcoin.it/wiki/Secp256k1
+  // p = FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFE FFFFFC2F
+  // P = 2256 - 232 - 29 - 28 - 27 - 26 - 24 - 1
+  if (curve === JwaCurve.Secp256k1) {
+    two = bigInt(2)
+    prime = two
+      .pow(256)
+      .subtract(two.pow(32))
+      .subtract(two.pow(9))
+      .subtract(two.pow(8))
+      .subtract(two.pow(7))
+      .subtract(two.pow(6))
+      .subtract(two.pow(4))
+      .subtract(1)
+    b = bigInt(7)
+    pIdent = prime.add(1).divide(4)
+  }
+
   if (!prime || !b || !pIdent) {
     throw new Error(`Unsupported curve ${curve}`)
   }
@@ -80,14 +100,20 @@ export function compress(publicKey: Uint8Array): Uint8Array {
   return compressECPoint(xOctet, yOctet)
 }
 
-export function expand(publicKey: Uint8Array, curve: 'P-256' | 'P-384' | 'P-521'): Uint8Array {
+export function expand(publicKey: Uint8Array, curve: 'P-256' | 'P-384' | 'P-521' | 'secp256k1'): Uint8Array {
   const publicKeyComponent = Buffer.from(publicKey).toString('hex')
   const { prime, b, pIdent } = getConstantsForCurve(curve)
   const signY = new Number(publicKeyComponent[1]).valueOf() - 2
   const x = bigInt(publicKeyComponent.substring(2), 16)
+
   // y^2 = x^3 - 3x + b
   let y = x.pow(3).subtract(x.multiply(3)).add(b).modPow(pIdent, prime)
 
+  if (curve === 'secp256k1') {
+    // y^2 = x^3 + 7
+    y = x.pow(3).add(7).modPow(pIdent, prime)
+  }
+
   // If the parity doesn't match it's the *other* root
   if (y.mod(2).toJSNumber() !== signY) {
     // y = prime - y

packages/core/src/crypto/jose/jwk/transform.ts

@@ -7,13 +7,14 @@ import { KeyType } from '../../KeyType'
 import { JwaCurve, JwaKeyType } from '../jwa'
 
 import { Ed25519Jwk } from './Ed25519Jwk'
+import { K256Jwk } from './K256Jwk'
 import { P256Jwk } from './P256Jwk'
 import { P384Jwk } from './P384Jwk'
 import { P521Jwk } from './P521Jwk'
 import { X25519Jwk } from './X25519Jwk'
 import { hasCrv } from './validate'
 
-const JwkClasses = [Ed25519Jwk, P256Jwk, P384Jwk, P521Jwk, X25519Jwk] as const
+const JwkClasses = [Ed25519Jwk, P256Jwk, P384Jwk, P521Jwk, X25519Jwk, K256Jwk] as const
 
 export function getJwkFromJson(jwkJson: JwkJson): Jwk {
   if (jwkJson.kty === JwaKeyType.OKP) {
@@ -25,6 +26,7 @@ export function getJwkFromJson(jwkJson: JwkJson): Jwk {
     if (hasCrv(jwkJson, JwaCurve.P256)) return P256Jwk.fromJson(jwkJson)
     if (hasCrv(jwkJson, JwaCurve.P384)) return P384Jwk.fromJson(jwkJson)
     if (hasCrv(jwkJson, JwaCurve.P521)) return P521Jwk.fromJson(jwkJson)
+    if (hasCrv(jwkJson, JwaCurve.Secp256k1)) return K256Jwk.fromJson(jwkJson)
   }
 
   throw new Error(`Cannot create JWK from JSON. Unsupported JWK with kty '${jwkJson.kty}'.`)
@@ -38,6 +40,8 @@ export function getJwkFromKey(key: Key) {
   if (key.keyType === KeyType.P384) return P384Jwk.fromPublicKey(key.publicKey)
   if (key.keyType === KeyType.P521) return P521Jwk.fromPublicKey(key.publicKey)
 
+  if (key.keyType === KeyType.K256) return K256Jwk.fromPublicKey(key.publicKey)
+
   throw new AriesFrameworkError(`Cannot create JWK from key. Unsupported key with type '${key.keyType}'.`)
 }
 

packages/core/src/crypto/keyUtils.ts

@@ -12,6 +12,7 @@ export function isValidSeed(seed: Buffer, keyType: KeyType): boolean {
     [KeyType.P256]: 64,
     [KeyType.P384]: 64,
     [KeyType.P521]: 64,
+    [KeyType.K256]: 64,
   } as const
 
   return Buffer.isBuffer(seed) && seed.length >= minimumSeedLength[keyType]
@@ -27,6 +28,7 @@ export function isValidPrivateKey(privateKey: Buffer, keyType: KeyType): boolean
     [KeyType.P256]: 32,
     [KeyType.P384]: 48,
     [KeyType.P521]: 66,
+    [KeyType.K256]: 32,
   } as const
 
   return Buffer.isBuffer(privateKey) && privateKey.length === privateKeyLength[keyType]
@@ -42,6 +44,7 @@ export function isSigningSupportedForKeyType(keyType: KeyType): boolean {
     [KeyType.Bls12381g1]: true,
     [KeyType.Bls12381g2]: true,
     [KeyType.Bls12381g1g2]: true,
+    [KeyType.K256]: true,
   } as const
 
   return keyTypeSigningSupportedMapping[keyType]
@@ -57,6 +60,7 @@ export function isEncryptionSupportedForKeyType(keyType: KeyType): boolean {
     [KeyType.Bls12381g1]: false,
     [KeyType.Bls12381g2]: false,
     [KeyType.Bls12381g1g2]: false,
+    [KeyType.K256]: true,
   } as const
 
   return keyTypeEncryptionSupportedMapping[keyType]

packages/core/src/crypto/multiCodecKey.ts

@@ -10,6 +10,7 @@ const multiCodecPrefixMap: Record<string, KeyType> = {
   4608: KeyType.P256,
   4609: KeyType.P384,
   4610: KeyType.P521,
+  231: KeyType.K256,
 }
 
 export function getKeyTypeByMultiCodecPrefix(multiCodecPrefix: number): KeyType {

packages/core/src/modules/dids/__tests__/__fixtures__/didKeyK256.json

@@ -0,0 +1,29 @@
+{
+  "@context": ["https://w3id.org/did/v1", "https://w3id.org/security/suites/jws-2020/v1"],
+  "id": "did:key:zQ3shjRPgHQQbTtXyofk1ygghRJ75RZpXmWBMY1BKnhyz7zKp",
+  "verificationMethod": [
+    {
+      "id": "did:key:zQ3shjRPgHQQbTtXyofk1ygghRJ75RZpXmWBMY1BKnhyz7zKp#zQ3shjRPgHQQbTtXyofk1ygghRJ75RZpXmWBMY1BKnhyz7zKp",
+      "type": "JsonWebKey2020",
+      "controller": "did:key:zQ3shjRPgHQQbTtXyofk1ygghRJ75RZpXmWBMY1BKnhyz7zKp",
+      "publicKeyJwk": {
+        "kty": "EC",
+        "crv": "secp256k1",
+        "x": "RwiZITTa2Dcmq-V1j-5tgPUshOLO31FbsnhVS-7lskc",
+        "y": "3o1-UCc3ABh757P58gDISSc4hOj9qyfSGl3SGGA7xdc"
+      }
+    }
+  ],
+  "authentication": [
+    "did:key:zQ3shjRPgHQQbTtXyofk1ygghRJ75RZpXmWBMY1BKnhyz7zKp#zQ3shjRPgHQQbTtXyofk1ygghRJ75RZpXmWBMY1BKnhyz7zKp"
+  ],
+  "assertionMethod": [
+    "did:key:zQ3shjRPgHQQbTtXyofk1ygghRJ75RZpXmWBMY1BKnhyz7zKp#zQ3shjRPgHQQbTtXyofk1ygghRJ75RZpXmWBMY1BKnhyz7zKp"
+  ],
+  "capabilityInvocation": [
+    "did:key:zQ3shjRPgHQQbTtXyofk1ygghRJ75RZpXmWBMY1BKnhyz7zKp#zQ3shjRPgHQQbTtXyofk1ygghRJ75RZpXmWBMY1BKnhyz7zKp"
+  ],
+  "capabilityDelegation": [
+    "did:key:zQ3shjRPgHQQbTtXyofk1ygghRJ75RZpXmWBMY1BKnhyz7zKp#zQ3shjRPgHQQbTtXyofk1ygghRJ75RZpXmWBMY1BKnhyz7zKp"
+  ]
+}

packages/core/src/modules/dids/domain/key-type/keyDidMapping.ts

@@ -34,6 +34,7 @@ const keyDidMapping: Record<KeyType, KeyDidMapping> = {
   [KeyType.P256]: keyDidJsonWebKey,
   [KeyType.P384]: keyDidJsonWebKey,
   [KeyType.P521]: keyDidJsonWebKey,
+  [KeyType.K256]: keyDidJsonWebKey,
 }
 
 /**

packages/core/src/modules/dids/domain/keyDidDocument.ts

@@ -27,6 +27,7 @@ const didDocumentKeyTypeMapping: Record<KeyType, (did: string, key: Key) => DidD
   [KeyType.P256]: getJsonWebKey2020DidDocument,
   [KeyType.P384]: getJsonWebKey2020DidDocument,
   [KeyType.P521]: getJsonWebKey2020DidDocument,
+  [KeyType.K256]: getJsonWebKey2020DidDocument,
 }
 
 export function getDidDocumentForKey(did: string, key: Key) {

packages/core/src/modules/dids/methods/key/__tests__/DidKey.test.ts

@@ -4,6 +4,7 @@ import didKeyBls12381g1 from '../../../__tests__/__fixtures__/didKeyBls12381g1.j
 import didKeyBls12381g1g2 from '../../../__tests__/__fixtures__/didKeyBls12381g1g2.json'
 import didKeyBls12381g2 from '../../../__tests__/__fixtures__/didKeyBls12381g2.json'
 import didKeyEd25519 from '../../../__tests__/__fixtures__/didKeyEd25519.json'
+import didKeyK256 from '../../../__tests__/__fixtures__/didKeyK256.json'
 import didKeyP256 from '../../../__tests__/__fixtures__/didKeyP256.json'
 import didKeyP384 from '../../../__tests__/__fixtures__/didKeyP384.json'
 import didKeyP521 from '../../../__tests__/__fixtures__/didKeyP521.json'
@@ -21,6 +22,7 @@ describe('DidKey', () => {
       didKeyP256,
       didKeyP384,
       didKeyP521,
+      didKeyK256,
     ]
 
     for (const documentType of documentTypes) {