Add repeating XOR encryption

basics.ts

@@ -103,3 +103,21 @@ export const detectSingleByteXor: DetectSingleByteXor = (buffs) => {
     candidates.sort((a, b) => b[0] - a[0]);
     return candidates[0][1];
 };
+
+type EncryptRepeatingXOR = (buff: Buffer, key: Buffer) => Buffer;
+export const encryptRepeatingXOR: EncryptRepeatingXOR = (buff, key) => {
+    const resBuff = Buffer.alloc(buff.length);
+    range(0, buff.length).forEach(i => {
+        resBuff[i] = buff[i] ^ key[i % key.length];
+    });
+    return resBuff;
+};
+
+type DecryptRepeatingXOR = (buff: Buffer, key: Buffer) => Buffer;
+export const decryptRepeatingXOR: DecryptRepeatingXOR = (buff, key) => {
+    const resBuff = Buffer.alloc(buff.length);
+    range(0, buff.length).forEach(i => {
+        resBuff[i] = buff[i] ^ key[i % key.length];
+    });
+    return resBuff;
+};