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Encrypting and Decrypting in go
package main
import (
"crypto/aes"
"crypto/cipher"
"crypto/rand"
"encoding/hex"
"fmt"
"io"
)
func main() {
bytes := make([]byte, 32) //generate a random 32 byte key for AES-256
if _, err := rand.Read(bytes); err != nil {
panic(err.Error())
}
key := hex.EncodeToString(bytes) //encode key in bytes to string and keep as secret, put in a vault
fmt.Printf("key to encrypt/decrypt : %s\n", key)
encrypted := encrypt("Hello Encrypt", key)
fmt.Printf("encrypted : %s\n", encrypted)
decrypted := decrypt(encrypted, key)
fmt.Printf("decrypted : %s\n", decrypted)
}
func encrypt(stringToEncrypt string, keyString string) (encryptedString string) {
//Since the key is in string, we need to convert decode it to bytes
key, _ := hex.DecodeString(keyString)
plaintext := []byte(stringToEncrypt)
//Create a new Cipher Block from the key
block, err := aes.NewCipher(key)
if err != nil {
panic(err.Error())
}
//Create a new GCM - https://en.wikipedia.org/wiki/Galois/Counter_Mode
//https://golang.org/pkg/crypto/cipher/#NewGCM
aesGCM, err := cipher.NewGCM(block)
if err != nil {
panic(err.Error())
}
//Create a nonce. Nonce should be from GCM
nonce := make([]byte, aesGCM.NonceSize())
if _, err = io.ReadFull(rand.Reader, nonce); err != nil {
panic(err.Error())
}
//Encrypt the data using aesGCM.Seal
//Since we don't want to save the nonce somewhere else in this case, we add it as a prefix to the encrypted data. The first nonce argument in Seal is the prefix.
ciphertext := aesGCM.Seal(nonce, nonce, plaintext, nil)
return fmt.Sprintf("%x", ciphertext)
}
func decrypt(encryptedString string, keyString string) (decryptedString string) {
key, _ := hex.DecodeString(keyString)
enc, _ := hex.DecodeString(encryptedString)
//Create a new Cipher Block from the key
block, err := aes.NewCipher(key)
if err != nil {
panic(err.Error())
}
//Create a new GCM
aesGCM, err := cipher.NewGCM(block)
if err != nil {
panic(err.Error())
}
//Get the nonce size
nonceSize := aesGCM.NonceSize()
//Extract the nonce from the encrypted data
nonce, ciphertext := enc[:nonceSize], enc[nonceSize:]
//Decrypt the data
plaintext, err := aesGCM.Open(nil, nonce, ciphertext, nil)
if err != nil {
panic(err.Error())
}
return fmt.Sprintf("%s", plaintext)
}
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