Improved XXTEA operations. Added XXTEA Decrypt.

src/core/lib/XXTEA.mjs

@@ -0,0 +1,174 @@
+/**
+ * XXTEA library
+ *
+ * Encryption Algorithm Authors:
+ *     David J. Wheeler
+ *     Roger M. Needham
+ *
+ * @author Ma Bingyao [mabingyao@gmail.com]
+ * @author n1474335 [n1474335@gmail.com]
+ * @license MIT
+ */
+
+const DELTA = 0x9E3779B9;
+
+/**
+ * Convert a buffer to a Uint8Array
+ * @param {Uint32Array} v
+ * @param {boolean} includeLength
+ * @returns {Uint8Array}
+ */
+function toUint8Array(v, includeLength) {
+    const length = v.length;
+    let n = length << 2;
+    if (includeLength) {
+        const m = v[length - 1];
+        n -= 4;
+        if ((m < n - 3) || (m > n)) {
+            return null;
+        }
+        n = m;
+    }
+    const bytes = new Uint8Array(n);
+    for (let i = 0; i < n; i++) {
+        bytes[i] = v[i >> 2] >> ((i & 3) << 3);
+    }
+    return bytes;
+}
+
+/**
+ * Convert a buffer to a Uint32Array
+ * @param {TypedArray} bs
+ * @param {boolean} includeLength
+ * @returns {Uint32Array}
+ */
+function toUint32Array(bs, includeLength) {
+    const length = bs.length;
+    let n = length >> 2;
+    if ((length & 3) !== 0) {
+        ++n;
+    }
+    let v;
+    if (includeLength) {
+        v = new Uint32Array(n + 1);
+        v[n] = length;
+    } else {
+        v = new Uint32Array(n);
+    }
+    for (let i = 0; i < length; ++i) {
+        v[i >> 2] |= bs[i] << ((i & 3) << 3);
+    }
+    return v;
+}
+
+/**
+ * Mask an int to 32 bits
+ * @param {number} i
+ * @returns {number}
+ */
+function int32(i) {
+    return i & 0xFFFFFFFF;
+}
+
+/**
+ * MX function for data randomisation
+ * @param {number} sum
+ * @param {number} y
+ * @param {number} z
+ * @param {number} p
+ * @param {number} e
+ * @param {number} k
+ * @returns {number}
+ */
+function mx(sum, y, z, p, e, k) {
+    return ((z >>> 5 ^ y << 2) + (y >>> 3 ^ z << 4)) ^ ((sum ^ y) + (k[p & 3 ^ e] ^ z));
+}
+
+/**
+ * Ensure an array is a multiple of 16 bits
+ * @param {TypedArray} k
+ * @returns {TypedArray}
+ */
+function fixk(k) {
+    if (k.length < 16) {
+        const key = new Uint8Array(16);
+        key.set(k);
+        return key;
+    }
+    return k;
+}
+
+/**
+ * Performs XXTEA encryption on a Uint32Array
+ * @param {Uint32Array} v
+ * @param {Uint32Array} k
+ * @returns {Uint32Array}
+ */
+function encryptUint32Array(v, k) {
+    const length = v.length;
+    const n = length - 1;
+    let y, z, sum, e, p, q;
+    z = v[n];
+    sum = 0;
+    for (q = Math.floor(6 + 52 / length) | 0; q > 0; --q) {
+        sum = int32(sum + DELTA);
+        e = sum >>> 2 & 3;
+        for (p = 0; p < n; ++p) {
+            y = v[p + 1];
+            z = v[p] = int32(v[p] + mx(sum, y, z, p, e, k));
+        }
+        y = v[0];
+        z = v[n] = int32(v[n] + mx(sum, y, z, n, e, k));
+    }
+    return v;
+}
+
+/**
+ * Performs XXTEA decryption on a Uint32Array
+ * @param {Uint32Array} v
+ * @param {Uint32Array} k
+ * @returns {Uint32Array}
+ */
+function decryptUint32Array(v, k) {
+    const length = v.length;
+    const n = length - 1;
+    let y, z, sum, e, p;
+    y = v[0];
+    const q = Math.floor(6 + 52 / length);
+    for (sum = int32(q * DELTA); sum !== 0; sum = int32(sum - DELTA)) {
+        e = sum >>> 2 & 3;
+        for (p = n; p > 0; --p) {
+            z = v[p - 1];
+            y = v[p] = int32(v[p] - mx(sum, y, z, p, e, k));
+        }
+        z = v[n];
+        y = v[0] = int32(v[0] - mx(sum, y, z, 0, e, k));
+    }
+    return v;
+}
+
+/**
+ * Encrypt function
+ * @param {TypedArray} data
+ * @param {TypedArray} key
+ * @returns {Uint8Array}
+ */
+export function encrypt(data, key) {
+    if (data === undefined || data === null || data.length === 0) {
+        return data;
+    }
+    return toUint8Array(encryptUint32Array(toUint32Array(data, true), toUint32Array(fixk(key), false)), false);
+}
+
+/**
+ * Decrypt function
+ * @param {TypedArray} data
+ * @param {TypedArray} key
+ * @returns {Uint8Array}
+ */
+export function decrypt(data, key) {
+    if (data === undefined || data === null || data.length === 0) {
+        return data;
+    }
+    return toUint8Array(decryptUint32Array(toUint32Array(data, false), toUint32Array(fixk(key), false)), true);
+}