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This simple program is to demonstrate encryption and decryption in golang using AES CBC with PKCS5Padding
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package main | |
import ( | |
"bytes" | |
"crypto/aes" | |
"crypto/cipher" | |
b64 "encoding/base64" | |
"errors" | |
"fmt" | |
"log" | |
) | |
var base64EncodedKeyBytes = "kV9Ld-X4rKlTQF4ZJwyn9A" | |
var base64EncodedIvBytes = "PCb_WQYrUgbahQeqDEkuUw" | |
func main() { | |
key, err1 := b64.RawURLEncoding.DecodeString(base64EncodedKeyBytes) | |
iv, err2 := b64.RawURLEncoding.DecodeString(base64EncodedIvBytes) | |
if err1 != nil || err2 != nil { | |
log.Fatal("Error decoding key/iv") | |
} | |
//plaintext := []byte("some really really really long plaintext") | |
//plaintext := []byte("testtesttesttest") | |
plaintext := []byte("test") | |
fmt.Printf("plaintext: %s\n", plaintext) | |
ciphertext, err := encrypt(key, iv, plaintext) | |
if err != nil { | |
log.Fatal(err) | |
} | |
fmt.Printf("encrypted: %s\n", ciphertext) | |
decrypted, err := decrypt(key, iv, ciphertext) | |
if err != nil { | |
log.Fatal(err) | |
} | |
fmt.Printf("decrypted: %s\n", decrypted) | |
} | |
func encrypt(key, iv, text []byte) (string, error) { | |
block, err := aes.NewCipher(key) | |
if err != nil { | |
return "", err | |
} | |
b := text | |
b = PKCS5Padding(b, aes.BlockSize, len(text)) | |
ciphertext := make([]byte, len(b)) | |
mode := cipher.NewCBCEncrypter(block, iv) | |
mode.CryptBlocks(ciphertext, b) | |
return b64.RawURLEncoding.EncodeToString(ciphertext), nil | |
} | |
func decrypt(key []byte, iv []byte, encText string) ([]byte, error) { | |
text, _ := b64.RawURLEncoding.DecodeString(encText) | |
block, err := aes.NewCipher(key) | |
if err != nil { | |
return nil, err | |
} | |
if len(text) < aes.BlockSize { | |
return nil, errors.New("ciphertext too short") | |
} | |
decrypted := make([]byte, len(text)) | |
mode := cipher.NewCBCDecrypter(block, iv) | |
mode.CryptBlocks(decrypted, text) | |
return PKCS5UnPadding(decrypted), nil | |
} | |
func PKCS5Padding(ciphertext []byte, blockSize int, after int) []byte { | |
padding := (blockSize - len(ciphertext)%blockSize) | |
padtext := bytes.Repeat([]byte{byte(padding)}, padding) | |
return append(ciphertext, padtext...) | |
} | |
func PKCS5UnPadding(src []byte) []byte { | |
length := len(src) | |
unpadding := int(src[length-1]) | |
return src[:(length - unpadding)] | |
} |
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