Keccak kdf

src/kdf.js

@@ -0,0 +1,40 @@
+const keccak = require('./keccak');
+
+function concatUint8Arrays(...arrays) {
+    let totalLength = arrays.reduce((acc, arr) => acc + arr.length, 0);
+    let result = new Uint8Array(totalLength);
+    let offset = 0;
+    for (const arr of arrays) {
+        result.set(arr, offset);
+        offset += arr.length;
+    }
+    return result;
+}
+
+
+class keccakKDF {
+    constructor(encryptionKeyLength = 32, privateKeyLength = 32) {
+        this.encryptionKeyLength = encryptionKeyLength;
+        this.privateKeyLength = privateKeyLength;
+    }
+    kdf(salt) {
+        const input = concatUint8Arrays(this.currentKey, salt);
+        const outputLength = this.encryptionKeyLength + this.privateKeyLength;
+        const output = keccak.SHAKE256(input, outputLength);
+        const encryptionKey = output.slice(0, this.encryptionKeyLength);
+        const newPrivateKey = output.slice(this.encryptionKeyLength, outputLength);
+        this.currentKey = newPrivateKey;
+        return encryptionKey;
+    }
+    init(initialKey, salt) {
+        this.currentKey = initialKey;
+        return this.kdf(salt);
+    }
+    next(salt) {
+        if (!this.currentKey) throw new Error("KDF not initialized");
+        return this.kdf(salt);
+    }
+
+}
+
+module.exports = { keccakKDF };