81 lines
2.2 KiB
Go
81 lines
2.2 KiB
Go
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// cryptopasta - basic cryptography examples
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//
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// Written in 2015 by George Tankersley <george.tankersley@gmail.com>
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//
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// To the extent possible under law, the author(s) have dedicated all copyright
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// and related and neighboring rights to this software to the public domain
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// worldwide. This software is distributed without any warranty.
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//
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// You should have received a copy of the CC0 Public Domain Dedication along
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// with this software. If not, see // <http://creativecommons.org/publicdomain/zero/1.0/>.
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// Provides symmetric authenticated encryption using 256-bit AES-GCM with a random nonce.
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package crypto
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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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"io"
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)
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// NewEncryptionKey generates a random 256-bit key for Encrypt() and
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// Decrypt(). It panics if the source of randomness fails.
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func NewEncryptionKey() [32]byte {
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key := [32]byte{}
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_, err := io.ReadFull(rand.Reader, key[:])
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if err != nil {
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panic(err)
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}
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return key
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}
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// Encrypt encrypts data using 256-bit AES-GCM. This both hides the content of
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// the data and provides a check that it hasn't been altered. Output takes the
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// form nonce|ciphertext|tag where '|' indicates concatenation.
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func Encrypt(plaintext []byte, key *[32]byte) (ciphertext []byte, err 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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_, err = io.ReadFull(rand.Reader, nonce)
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if err != nil {
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return nil, err
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}
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return gcm.Seal(nonce, nonce, plaintext, nil), nil
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}
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// Decrypt decrypts data using 256-bit AES-GCM. This both hides the content of
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// the data and provides a check that it hasn't been altered. Expects input
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// form nonce|ciphertext|tag where '|' indicates concatenation.
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func Decrypt(ciphertext []byte, key *[32]byte) (plaintext []byte, err 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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if len(ciphertext) < gcm.NonceSize() {
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return nil, errors.New("malformed ciphertext")
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}
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return gcm.Open(nil,
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ciphertext[:gcm.NonceSize()],
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ciphertext[gcm.NonceSize():],
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nil,
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)
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}
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