move some more crypto to taler-util package

1 files changed, 17 insertions, 2 deletions

diff --git a/packages/taler-util/src/kdf.ts b/packages/taler-util/src/kdf.ts
index af4d05035..7710de90c 100644
--- a/packages/taler-util/src/kdf.ts
+++ b/packages/taler-util/src/kdf.ts
@@ -59,15 +59,30 @@ export function hmacSha256(key: Uint8Array, message: Uint8Array): Uint8Array {
   return hmac(sha256, 64, key, message);
 }
 
+/**
+ * HMAC-SHA512-SHA256 (see RFC 5869).
+ */
+export function kdfKw(args: {
+  outputLength: number;
+  ikm: Uint8Array;
+  salt?: Uint8Array;
+  info?: Uint8Array;
+}) {
+  return kdf(args.outputLength, args.ikm, args.salt, args.info);
+}
+
 export function kdf(
   outputLength: number,
   ikm: Uint8Array,
-  salt: Uint8Array,
-  info: Uint8Array,
+  salt?: Uint8Array,
+  info?: Uint8Array,
 ): Uint8Array {
+  salt = salt ?? new Uint8Array(64);
   // extract
   const prk = hmacSha512(salt, ikm);
 
+  info = info ?? new Uint8Array(0);
+
   // expand
   const N = Math.ceil(outputLength / 32);
   const output = new Uint8Array(N * 32);