73 lines
1.7 KiB
Go
73 lines
1.7 KiB
Go
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// Package keygen provides the AES key initializer function.
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package keygen
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import (
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"crypto/aes"
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"crypto/cipher"
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"crypto/rand"
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"errors"
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"fmt"
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"io"
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)
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// NewAESKey returns a 32-byte (AES 256 bit) encryption key.
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func NewAESKey() ([]byte, error) {
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var result = make([]byte, 32)
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_, err := rand.Read(result)
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return result, err
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}
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// EncryptWithAESKey a byte stream using a given AES key.
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func EncryptWithAESKey(input []byte, key []byte) ([]byte, error) {
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// Generate a new AES cipher.
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c, err := aes.NewCipher(key)
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if err != nil {
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return nil, err
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}
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// gcm or Galois/Counter Mode
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gcm, err := cipher.NewGCM(c)
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if err != nil {
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return nil, err
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}
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// Create a new byte array the size of the GCM nonce
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// which must be passed to Seal.
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nonce := make([]byte, gcm.NonceSize())
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if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
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return nil, fmt.Errorf("populating the nonce: %s", err)
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}
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// Encrypt the text using the Seal function.
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// Seal encrypts and authenticates plaintext, authenticates the
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// additional data and appends the result to dst, returning the
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// updated slice. The nonce must be NonceSize() bytes long and
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// unique for all time, for a given key.
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result := gcm.Seal(nonce, nonce, input, nil)
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return result, nil
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}
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func DecryptWithAESKey(data []byte, key []byte) ([]byte, error) {
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c, err := aes.NewCipher(key)
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if err != nil {
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return nil, err
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}
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gcm, err := cipher.NewGCM(c)
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if err != nil {
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return nil, err
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}
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nonceSize := gcm.NonceSize()
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if len(data) < nonceSize {
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return nil, errors.New("ciphertext data less than nonceSize")
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}
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nonce, ciphertext := data[:nonceSize], data[nonceSize:]
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plaintext, err := gcm.Open(nil, nonce, ciphertext, nil)
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if err != nil {
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return nil, err
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}
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return plaintext, nil
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}
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