ox
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JavaScript
import * as Cbor from './Cbor.js';
import * as Errors from './Errors.js';
import * as PublicKey from './PublicKey.js';
/**
* Converts a P256 {@link ox#PublicKey.PublicKey} to a CBOR-encoded COSE_Key.
*
* The COSE_Key uses integer map keys per [RFC 9053](https://datatracker.ietf.org/doc/html/rfc9053):
* - `1` (kty): `2` (EC2)
* - `3` (alg): `-7` (ES256)
* - `-1` (crv): `1` (P-256)
* - `-2` (x): x coordinate bytes
* - `-3` (y): y coordinate bytes
*
* @example
* ```ts twoslash
* import { CoseKey, P256 } from 'ox'
*
* const { publicKey } = P256.createKeyPair()
*
* const coseKey = CoseKey.fromPublicKey(publicKey)
* ```
*
* @param publicKey - The P256 public key to convert.
* @returns The CBOR-encoded COSE_Key as a Hex string.
*/
export function fromPublicKey(publicKey) {
const pkBytes = PublicKey.toBytes(publicKey);
const x = pkBytes.slice(1, 33);
const y = pkBytes.slice(33, 65);
return Cbor.encode(new Map([
[1, 2], // kty: EC2
[3, -7], // alg: ES256
[-1, 1], // crv: P-256
[-2, x], // x coordinate
[-3, y], // y coordinate
]));
}
/**
* Converts a CBOR-encoded COSE_Key to a P256 {@link ox#PublicKey.PublicKey}.
*
* @example
* ```ts twoslash
* import { CoseKey, P256 } from 'ox'
*
* const { publicKey } = P256.createKeyPair()
* const coseKey = CoseKey.fromPublicKey(publicKey)
*
* const publicKey2 = CoseKey.toPublicKey(coseKey)
* ```
*
* @param coseKey - The CBOR-encoded COSE_Key.
* @returns The P256 public key.
*/
export function toPublicKey(coseKey) {
const decoded = Cbor.decode(coseKey);
const x = decoded['-2'];
const y = decoded['-3'];
if (!(x instanceof Uint8Array) || !(y instanceof Uint8Array))
throw new InvalidCoseKeyError();
return PublicKey.from(new Uint8Array([0x04, ...x, ...y]));
}
/** Thrown when a COSE_Key does not contain valid P256 public key coordinates. */
export class InvalidCoseKeyError extends Errors.BaseError {
constructor() {
super('COSE_Key does not contain valid P256 public key coordinates.');
Object.defineProperty(this, "name", {
enumerable: true,
configurable: true,
writable: true,
value: 'CoseKey.InvalidCoseKeyError'
});
}
}
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