Remove unnecessary usages from public and private keys.

Author: msporny

lib/mldsa.js

@@ -21,13 +21,11 @@ export function generateKey({algorithm} = {}) {
     publicKey: {
       type: 'public',
       algorithm,
-      usages: ['verify'],
       _keyBytes: pubBytes,
     },
     secretKey: {
       type: 'private',
       algorithm,
-      usages: ['sign'],
       _keyBytes: secBytes,
       _seedBytes: seed,
     }
@@ -36,7 +34,7 @@ export function generateKey({algorithm} = {}) {
 
 // Signs data using ML-DSA.
 export function sign({secretKey, data} = {}) {
-  _assertKey(secretKey, 'private', 'sign');
+  _assertKey(secretKey, 'private');
   const {impl} = _getImpl(secretKey.algorithm);
   const msg = _toUint8Array(data);
   const sig = impl.sign(msg, secretKey._keyBytes);
@@ -45,7 +43,7 @@ export function sign({secretKey, data} = {}) {
 
 // Verifies a signature over data using ML-DSA.
 export function verify({publicKey, signature, data} = {}) {
-  _assertKey(publicKey, 'public', 'verify');
+  _assertKey(publicKey, 'public');
   const {impl} = _getImpl(publicKey.algorithm);
   const msg = _toUint8Array(data);
   const sig = _toUint8Array(signature);
@@ -64,7 +62,6 @@ export function importKey({format, keyData, algorithm} = {}) {
     return {
       type: 'public',
       algorithm,
-      usages: ['verify'],
       _keyBytes: _toUint8Array(keyData),
     };
   }
@@ -75,7 +72,6 @@ export function importKey({format, keyData, algorithm} = {}) {
     return {
       type: 'private',
       algorithm,
-      usages: ['sign'],
       _keyBytes: secBytes,
       _seedBytes: seedBytes,
     };
@@ -93,7 +89,7 @@ export function exportKeyAsJwk({key} = {}) {
   const jwk = {
     kty: 'AKP',
     alg: key.algorithm,
-    key_ops: key.usages,
+    key_ops: key.type === 'public' ? ['verify'] : ['sign'],
     ext: true,
   };
   if(key.type === 'public') {
@@ -112,16 +108,13 @@ function _getImpl(algorithm) {
   return entry;
 }
 
-function _assertKey(key, expectedType, expectedUsage) {
+function _assertKey(key, expectedType) {
   if(!key || typeof key !== 'object') {
     throw new TypeError('Invalid key.');
   }
   if(key.type !== expectedType) {
     throw new TypeError(`Expected a ${expectedType} key.`);
   }
-  if(!key.usages.includes(expectedUsage)) {
-    throw new TypeError(`Key does not have "${expectedUsage}" usage.`);
-  }
 }
 
 function _toUint8Array(data) {
@@ -157,7 +150,6 @@ function _importJwk({jwk, algorithm, impl}) {
     return {
       type: 'private',
       algorithm,
-      usages: ['sign'],
       _keyBytes: secBytes,
       _seedBytes: seedBytes,
     };
@@ -169,7 +161,6 @@ function _importJwk({jwk, algorithm, impl}) {
   return {
     type: 'public',
     algorithm,
-    usages: ['verify'],
     _keyBytes: base64url.decode(jwk.pub),
   };
 }