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December 20, 2023 15:49
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Golang AES GCM Encrypt String and File example
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| package main | |
| import ( | |
| "crypto/aes" | |
| "crypto/cipher" | |
| "crypto/rand" | |
| "io" | |
| "io/ioutil" | |
| "log" | |
| "os" | |
| "fmt" | |
| "encoding/hex" | |
| ) | |
| func main() { | |
| os.Remove("assets/ciphertext.bin") | |
| os.Remove("assets/outputs/plaintext.txt") | |
| encryptFile() | |
| decryptFile() | |
| decryptString( encryptString("sun moon dog cat cow moon sea breeze foundation") ) | |
| } | |
| func encryptFile() { | |
| // Reading plaintext file | |
| plainText, err := ioutil.ReadFile("assets/plaintext.txt") | |
| if err != nil { | |
| log.Fatalf("read file err: %v", err.Error()) | |
| } | |
| // Reading key | |
| key, err := ioutil.ReadFile("assets/key.txt") | |
| if err != nil { | |
| log.Fatalf("read file err: %v", err.Error()) | |
| } | |
| // Creating block of algorithm | |
| block, err := aes.NewCipher(key) | |
| if err != nil { | |
| log.Fatalf("cipher err: %v", err.Error()) | |
| } | |
| // Creating GCM mode | |
| gcm, err := cipher.NewGCM(block) | |
| if err != nil { | |
| log.Fatalf("cipher GCM err: %v", err.Error()) | |
| } | |
| // Generating random nonce | |
| nonce := make([]byte, gcm.NonceSize()) | |
| if _, err := io.ReadFull(rand.Reader, nonce); err != nil { | |
| log.Fatalf("nonce err: %v", err.Error()) | |
| } | |
| // Encrypt file | |
| cipherText := gcm.Seal(nonce, nonce, plainText, nil) | |
| // Writing ciphertext file | |
| err = ioutil.WriteFile("assets/encrypted_cipherText.bin", cipherText, 0777) | |
| if err != nil { | |
| log.Fatalf("write file err: %v", err.Error()) | |
| } | |
| } | |
| func decryptFile() { | |
| // Reading ciphertext file | |
| cipherText, err := ioutil.ReadFile("assets/encrypted_cipherText.bin") | |
| if err != nil { | |
| log.Fatal(err) | |
| } | |
| // Reading key | |
| key, err := ioutil.ReadFile("assets/key.txt") | |
| if err != nil { | |
| log.Fatalf("read file err: %v", err.Error()) | |
| } | |
| // Creating block of algorithm | |
| block, err := aes.NewCipher(key) | |
| if err != nil { | |
| log.Fatalf("cipher err: %v", err.Error()) | |
| } | |
| // Creating GCM mode | |
| gcm, err := cipher.NewGCM(block) | |
| if err != nil { | |
| log.Fatalf("cipher GCM err: %v", err.Error()) | |
| } | |
| // Deattached nonce and decrypt | |
| nonce := cipherText[:gcm.NonceSize()] | |
| cipherText = cipherText[gcm.NonceSize():] | |
| plainText, err := gcm.Open(nil, nonce, cipherText, nil) | |
| if err != nil { | |
| log.Fatalf("decrypt file err: %v", err.Error()) | |
| } | |
| // Writing decryption content | |
| err = ioutil.WriteFile("assets/outputs/plaintext.txt", plainText, 0777) | |
| if err != nil { | |
| log.Fatalf("write file err: %v", err.Error()) | |
| } | |
| } | |
| func encryptString(plainString string) []byte { | |
| key, _ := hex.DecodeString("6368616e676520746869732070617373") | |
| plaintext := []byte(plainString) | |
| block, err := aes.NewCipher(key) | |
| if err != nil { | |
| panic(err.Error()) | |
| } | |
| aesgcm, err := cipher.NewGCM(block) | |
| if err != nil { | |
| panic(err.Error()) | |
| } | |
| // Never use more than 2^32 random nonces with a given key because of the risk of a repeat. | |
| nonce := make([]byte, aesgcm.NonceSize()) | |
| if _, err := io.ReadFull(rand.Reader, nonce); err != nil { | |
| panic(err.Error()) | |
| } | |
| ciphertext := aesgcm.Seal(nil, nonce, plaintext, nil) | |
| ciphertext = append(nonce, ciphertext...) | |
| fmt.Printf("encryptString to: %x\n", ciphertext) | |
| return ciphertext | |
| } | |
| func decryptString(cipherText []byte) { | |
| key, _ := hex.DecodeString("6368616e676520746869732070617373") | |
| // Creating block of algorithm | |
| block, err := aes.NewCipher(key) | |
| if err != nil { | |
| log.Fatalf("cipher err: %v", err.Error()) | |
| } | |
| // Creating GCM mode | |
| gcm, err := cipher.NewGCM(block) | |
| if err != nil { | |
| log.Fatalf("cipher GCM err: %v", err.Error()) | |
| } | |
| // Deattached nonce and decrypt | |
| nonce := cipherText[:gcm.NonceSize()] | |
| cipherText = cipherText[gcm.NonceSize():] | |
| plainText, err := gcm.Open(nil, nonce, cipherText, nil) | |
| if err != nil { | |
| log.Fatalf("decrypt cipher text err: %v", err.Error()) | |
| } | |
| // Writing decryption content | |
| fmt.Printf("%s\n", plainText) | |
| } |
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