Adding DES encryption and decryption methods

des.go

@@ -0,0 +1,59 @@
+package crsuite
+
+import (
+	"bytes"
+	"crypto/cipher"
+	"crypto/des"
+)
+
+// DESEncrypt performs DES encryption on plaintext using key and iv, and returns
+// the ciphertext.
+func DESEncrypt(plaintext []byte, key []byte, iv []byte) ([]byte, error) {
+
+	block, blkErr := des.NewCipher(key)
+	if blkErr != nil {
+		return nil, blkErr
+	}
+
+	blockSize := block.BlockSize()
+	originalData := PKCS5Padding(plaintext, blockSize)
+	blockMode := cipher.NewCBCEncrypter(block, iv)
+	ciphertext := make([]byte, len(originalData))
+	blockMode.CryptBlocks(ciphertext, originalData)
+	return ciphertext, nil
+}
+
+// DESDecrypt performs DES decryption on ciphertext using key and iv, and
+// returns the decrypted plaintext thus obtained.
+func DESDecrypt(ciphertext []byte, key []byte, iv []byte) ([]byte, error) {
+	block, err := des.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+
+	blockMode := cipher.NewCBCDecrypter(block, iv)
+	originalData := make([]byte, len(ciphertext))
+	blockMode.CryptBlocks(originalData, ciphertext)
+	originalData = PKCS5UnPadding(originalData)
+	return originalData, nil
+}
+
+// PKCS5Padding adds padding to src using the PKCS5 padding schema described in
+// RFC 2898.
+//
+// Reference: https://www.ietf.org/rfc/rfc2898.txt
+func PKCS5Padding(src []byte, blockSize int) []byte {
+	padding := blockSize - len(src)%blockSize
+	padtext := bytes.Repeat([]byte{byte(padding)}, padding)
+	return append(src, padtext...)
+}
+
+// PKCS5Padding removes padding from src according to the PKCS5 padding schema
+// described in RFC 2898.
+//
+// Reference: https://www.ietf.org/rfc/rfc2898.txt
+func PKCS5UnPadding(src []byte) []byte {
+	length := len(src)
+	unpadding := int(src[length-1])
+	return src[:(length - unpadding)]
+}

rsa.go

@@ -4,12 +4,13 @@ import (
 	"crypto"
 	"crypto/rand"
 	"crypto/rsa"
-    "crypto/sha256"
+	"crypto/sha256"
 )
+
 // RSAEncrypt encrypts plaintext using the RSA (Rivest–Shamir–Adleman)
 // encryption algorithm.
 func RSAEncrypt(plaintext []byte, keySize int) (ciphertext []byte, publicKey *rsa.PublicKey, privateKey *rsa.PrivateKey, err error) {
-    privateKey, err = GenerateKeyPairs(keySize)
+	privateKey, err = GenerateKeyPairs(keySize)
 	if err != nil {
 		return
 	}
@@ -23,7 +24,7 @@ func RSAEncrypt(plaintext []byte, keySize int) (ciphertext []byte, publicKey *rs
 // RSADecrypt decrypts ciphertext using privateKey and returns the plaintext
 // thus obtained.
 func RSADecrypt(ciphertext []byte, privateKey *rsa.PrivateKey) ([]byte, error) {
-    return privateKey.Decrypt(nil, ciphertext, &rsa.OAEPOptions{Hash: crypto.SHA256})
+	return privateKey.Decrypt(nil, ciphertext, &rsa.OAEPOptions{Hash: crypto.SHA256})
 }
 
 // GenerateKeyPairs generates private and public keys for RSA encryption.