73 lines
1.7 KiB
Go
73 lines
1.7 KiB
Go
package crypto
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import (
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"crypto/aes"
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"crypto/cipher"
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"crypto/hmac"
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"crypto/rand"
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"crypto/sha256"
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"encoding/hex"
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"fmt"
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"io"
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)
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// Encrypt encrypts plaintext using AES-GCM with the provided key.
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// The key must be 32 bytes (AES-256).
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func Encrypt(plaintext []byte, key []byte) ([]byte, error) {
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block, 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(block)
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if err != nil {
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return nil, err
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}
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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, err
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}
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// Seal appends the ciphertext to the nonce, so we return [nonce][ciphertext]
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return gcm.Seal(nonce, nonce, plaintext, nil), nil
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}
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// Decrypt decrypts ciphertext using AES-GCM with the provided key.
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func Decrypt(ciphertext []byte, key []byte) ([]byte, error) {
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block, 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(block)
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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(ciphertext) < nonceSize {
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return nil, fmt.Errorf("ciphertext too short")
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}
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nonce, actualCiphertext := ciphertext[:nonceSize], ciphertext[nonceSize:]
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return gcm.Open(nil, nonce, actualCiphertext, nil)
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}
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// GenerateBlindIndex creates a deterministic HMAC-SHA256 hash of a value.
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// This allows searching for encrypted data without knowing the plaintext.
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func GenerateBlindIndex(value string, salt []byte) string {
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h := hmac.New(sha256.New, salt)
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h.Write([]byte(value))
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return hex.EncodeToString(h.Sum(nil))
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}
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// GenerateKey generates a random 32-byte key.
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func GenerateKey() ([]byte, error) {
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key := make([]byte, 32)
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if _, err := io.ReadFull(rand.Reader, key); err != nil {
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return nil, err
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}
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return key, nil
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}
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