crypto/cipher: add one-time pad encrypt and decrypt

src/crypto/cipher/otp.go

@@ -0,0 +1,30 @@
+package cipher
+
+import "crypto/rand"
+
+func KeyGen(message string) []byte {
+	key := make([]byte, len(message))
+
+	_, err := rand.Read(key)
+	if err != nil {
+		panic(err)
+	}
+	return key
+}
+
+func OTPEncrypt(message string) (encrypted, key []byte) {
+	encrypted = make([]byte, len(message))
+	key = KeyGen(message)
+	for i := 0; i < len(message); i++ {
+		encrypted[i] = message[i] ^ key[i]
+	}
+	return
+}
+
+func OTPDecrypt(encrypted, key []byte) []byte {
+	decrypted := make([]byte, len(encrypted))
+	for i := 0; i < len(encrypted); i++ {
+		decrypted[i] = encrypted[i] ^ key[i]
+	}
+	return decrypted
+}

src/crypto/cipher/otp_test.go

@@ -0,0 +1,16 @@
+package cipher
+
+import (
+	"bytes"
+	"testing"
+)
+
+func TestOTP(t *testing.T) {
+	msg := []byte("Hello OTP!")
+	ciphertext, key := OTPEncrypt(string(msg))
+	decrypted := OTPDecrypt(ciphertext, key)
+
+	if !bytes.Equal([]byte(decrypted), msg) {
+		t.Errorf("Decrypted message does not match original")
+	}
+}