package cipher

Import Path
	crypto/cipher (on go.dev)

Dependency Relation
	imports 5 packages, and imported by 8 packages

Involved Source Files cbc.go cfb.go Package cipher implements standard block cipher modes that can be wrapped around low-level block cipher implementations. See https://csrc.nist.gov/groups/ST/toolkit/BCM/current_modes.html and NIST Special Publication 800-38A. ctr.go gcm.go io.go ofb.go xor_amd64.go xor_amd64.s
Code Examples package main import ( "crypto/aes" "crypto/cipher" "encoding/hex" "fmt" ) func main() { // Load your secret key from a safe place and reuse it across multiple // NewCipher calls. (Obviously don't use this example key for anything // real.) If you want to convert a passphrase to a key, use a suitable // package like bcrypt or scrypt. key, _ := hex.DecodeString("6368616e676520746869732070617373") ciphertext, _ := hex.DecodeString("73c86d43a9d700a253a96c85b0f6b03ac9792e0e757f869cca306bd3cba1c62b") block, err := aes.NewCipher(key) if err != nil { panic(err) } // The IV needs to be unique, but not secure. Therefore it's common to // include it at the beginning of the ciphertext. if len(ciphertext) < aes.BlockSize { panic("ciphertext too short") } iv := ciphertext[:aes.BlockSize] ciphertext = ciphertext[aes.BlockSize:] // CBC mode always works in whole blocks. if len(ciphertext)%aes.BlockSize != 0 { panic("ciphertext is not a multiple of the block size") } mode := cipher.NewCBCDecrypter(block, iv) // CryptBlocks can work in-place if the two arguments are the same. mode.CryptBlocks(ciphertext, ciphertext) // If the original plaintext lengths are not a multiple of the block // size, padding would have to be added when encrypting, which would be // removed at this point. For an example, see // https://tools.ietf.org/html/rfc5246#section-6.2.3.2. However, it's // critical to note that ciphertexts must be authenticated (i.e. by // using crypto/hmac) before being decrypted in order to avoid creating // a padding oracle. fmt.Printf("%s\n", ciphertext) } package main import ( "crypto/aes" "crypto/cipher" "crypto/rand" "encoding/hex" "fmt" "io" ) func main() { // Load your secret key from a safe place and reuse it across multiple // NewCipher calls. (Obviously don't use this example key for anything // real.) If you want to convert a passphrase to a key, use a suitable // package like bcrypt or scrypt. key, _ := hex.DecodeString("6368616e676520746869732070617373") plaintext := []byte("exampleplaintext") // CBC mode works on blocks so plaintexts may need to be padded to the // next whole block. For an example of such padding, see // https://tools.ietf.org/html/rfc5246#section-6.2.3.2. Here we'll // assume that the plaintext is already of the correct length. if len(plaintext)%aes.BlockSize != 0 { panic("plaintext is not a multiple of the block size") } block, err := aes.NewCipher(key) if err != nil { panic(err) } // The IV needs to be unique, but not secure. Therefore it's common to // include it at the beginning of the ciphertext. ciphertext := make([]byte, aes.BlockSize+len(plaintext)) iv := ciphertext[:aes.BlockSize] if _, err := io.ReadFull(rand.Reader, iv); err != nil { panic(err) } mode := cipher.NewCBCEncrypter(block, iv) mode.CryptBlocks(ciphertext[aes.BlockSize:], plaintext) // It's important to remember that ciphertexts must be authenticated // (i.e. by using crypto/hmac) as well as being encrypted in order to // be secure. fmt.Printf("%x\n", ciphertext) } package main import ( "crypto/aes" "crypto/cipher" "encoding/hex" "fmt" ) func main() { // Load your secret key from a safe place and reuse it across multiple // NewCipher calls. (Obviously don't use this example key for anything // real.) If you want to convert a passphrase to a key, use a suitable // package like bcrypt or scrypt. key, _ := hex.DecodeString("6368616e676520746869732070617373") ciphertext, _ := hex.DecodeString("7dd015f06bec7f1b8f6559dad89f4131da62261786845100056b353194ad") block, err := aes.NewCipher(key) if err != nil { panic(err) } // The IV needs to be unique, but not secure. Therefore it's common to // include it at the beginning of the ciphertext. if len(ciphertext) < aes.BlockSize { panic("ciphertext too short") } iv := ciphertext[:aes.BlockSize] ciphertext = ciphertext[aes.BlockSize:] stream := cipher.NewCFBDecrypter(block, iv) // XORKeyStream can work in-place if the two arguments are the same. stream.XORKeyStream(ciphertext, ciphertext) fmt.Printf("%s", ciphertext) } package main import ( "crypto/aes" "crypto/cipher" "crypto/rand" "encoding/hex" "fmt" "io" ) func main() { // Load your secret key from a safe place and reuse it across multiple // NewCipher calls. (Obviously don't use this example key for anything // real.) If you want to convert a passphrase to a key, use a suitable // package like bcrypt or scrypt. key, _ := hex.DecodeString("6368616e676520746869732070617373") plaintext := []byte("some plaintext") block, err := aes.NewCipher(key) if err != nil { panic(err) } // The IV needs to be unique, but not secure. Therefore it's common to // include it at the beginning of the ciphertext. ciphertext := make([]byte, aes.BlockSize+len(plaintext)) iv := ciphertext[:aes.BlockSize] if _, err := io.ReadFull(rand.Reader, iv); err != nil { panic(err) } stream := cipher.NewCFBEncrypter(block, iv) stream.XORKeyStream(ciphertext[aes.BlockSize:], plaintext) // It's important to remember that ciphertexts must be authenticated // (i.e. by using crypto/hmac) as well as being encrypted in order to // be secure. fmt.Printf("%x\n", ciphertext) } package main import ( "crypto/aes" "crypto/cipher" "crypto/rand" "encoding/hex" "fmt" "io" ) func main() { // Load your secret key from a safe place and reuse it across multiple // NewCipher calls. (Obviously don't use this example key for anything // real.) If you want to convert a passphrase to a key, use a suitable // package like bcrypt or scrypt. key, _ := hex.DecodeString("6368616e676520746869732070617373") plaintext := []byte("some plaintext") block, err := aes.NewCipher(key) if err != nil { panic(err) } // The IV needs to be unique, but not secure. Therefore it's common to // include it at the beginning of the ciphertext. ciphertext := make([]byte, aes.BlockSize+len(plaintext)) iv := ciphertext[:aes.BlockSize] if _, err := io.ReadFull(rand.Reader, iv); err != nil { panic(err) } stream := cipher.NewCTR(block, iv) stream.XORKeyStream(ciphertext[aes.BlockSize:], plaintext) // It's important to remember that ciphertexts must be authenticated // (i.e. by using crypto/hmac) as well as being encrypted in order to // be secure. // CTR mode is the same for both encryption and decryption, so we can // also decrypt that ciphertext with NewCTR. plaintext2 := make([]byte, len(plaintext)) stream = cipher.NewCTR(block, iv) stream.XORKeyStream(plaintext2, ciphertext[aes.BlockSize:]) fmt.Printf("%s\n", plaintext2) } package main import ( "crypto/aes" "crypto/cipher" "encoding/hex" "fmt" ) func main() { // Load your secret key from a safe place and reuse it across multiple // Seal/Open calls. (Obviously don't use this example key for anything // real.) If you want to convert a passphrase to a key, use a suitable // package like bcrypt or scrypt. // When decoded the key should be 16 bytes (AES-128) or 32 (AES-256). key, _ := hex.DecodeString("6368616e676520746869732070617373776f726420746f206120736563726574") ciphertext, _ := hex.DecodeString("c3aaa29f002ca75870806e44086700f62ce4d43e902b3888e23ceff797a7a471") nonce, _ := hex.DecodeString("64a9433eae7ccceee2fc0eda") block, err := aes.NewCipher(key) if err != nil { panic(err.Error()) } aesgcm, err := cipher.NewGCM(block) if err != nil { panic(err.Error()) } plaintext, err := aesgcm.Open(nil, nonce, ciphertext, nil) if err != nil { panic(err.Error()) } fmt.Printf("%s\n", plaintext) } package main import ( "crypto/aes" "crypto/cipher" "crypto/rand" "encoding/hex" "fmt" "io" ) func main() { // Load your secret key from a safe place and reuse it across multiple // Seal/Open calls. (Obviously don't use this example key for anything // real.) If you want to convert a passphrase to a key, use a suitable // package like bcrypt or scrypt. // When decoded the key should be 16 bytes (AES-128) or 32 (AES-256). key, _ := hex.DecodeString("6368616e676520746869732070617373776f726420746f206120736563726574") plaintext := []byte("exampleplaintext") block, err := aes.NewCipher(key) 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, 12) if _, err := io.ReadFull(rand.Reader, nonce); err != nil { panic(err.Error()) } aesgcm, err := cipher.NewGCM(block) if err != nil { panic(err.Error()) } ciphertext := aesgcm.Seal(nil, nonce, plaintext, nil) fmt.Printf("%x\n", ciphertext) } package main import ( "crypto/aes" "crypto/cipher" "crypto/rand" "encoding/hex" "fmt" "io" ) func main() { // Load your secret key from a safe place and reuse it across multiple // NewCipher calls. (Obviously don't use this example key for anything // real.) If you want to convert a passphrase to a key, use a suitable // package like bcrypt or scrypt. key, _ := hex.DecodeString("6368616e676520746869732070617373") plaintext := []byte("some plaintext") block, err := aes.NewCipher(key) if err != nil { panic(err) } // The IV needs to be unique, but not secure. Therefore it's common to // include it at the beginning of the ciphertext. ciphertext := make([]byte, aes.BlockSize+len(plaintext)) iv := ciphertext[:aes.BlockSize] if _, err := io.ReadFull(rand.Reader, iv); err != nil { panic(err) } stream := cipher.NewOFB(block, iv) stream.XORKeyStream(ciphertext[aes.BlockSize:], plaintext) // It's important to remember that ciphertexts must be authenticated // (i.e. by using crypto/hmac) as well as being encrypted in order to // be secure. // OFB mode is the same for both encryption and decryption, so we can // also decrypt that ciphertext with NewOFB. plaintext2 := make([]byte, len(plaintext)) stream = cipher.NewOFB(block, iv) stream.XORKeyStream(plaintext2, ciphertext[aes.BlockSize:]) fmt.Printf("%s\n", plaintext2) } package main import ( "bytes" "crypto/aes" "crypto/cipher" "encoding/hex" "io" "os" ) func main() { // Load your secret key from a safe place and reuse it across multiple // NewCipher calls. (Obviously don't use this example key for anything // real.) If you want to convert a passphrase to a key, use a suitable // package like bcrypt or scrypt. key, _ := hex.DecodeString("6368616e676520746869732070617373") encrypted, _ := hex.DecodeString("cf0495cc6f75dafc23948538e79904a9") bReader := bytes.NewReader(encrypted) block, err := aes.NewCipher(key) if err != nil { panic(err) } // If the key is unique for each ciphertext, then it's ok to use a zero // IV. var iv [aes.BlockSize]byte stream := cipher.NewOFB(block, iv[:]) reader := &cipher.StreamReader{S: stream, R: bReader} // Copy the input to the output stream, decrypting as we go. if _, err := io.Copy(os.Stdout, reader); err != nil { panic(err) } // Note that this example is simplistic in that it omits any // authentication of the encrypted data. If you were actually to use // StreamReader in this manner, an attacker could flip arbitrary bits in // the output. } package main import ( "bytes" "crypto/aes" "crypto/cipher" "encoding/hex" "fmt" "io" ) func main() { // Load your secret key from a safe place and reuse it across multiple // NewCipher calls. (Obviously don't use this example key for anything // real.) If you want to convert a passphrase to a key, use a suitable // package like bcrypt or scrypt. key, _ := hex.DecodeString("6368616e676520746869732070617373") bReader := bytes.NewReader([]byte("some secret text")) block, err := aes.NewCipher(key) if err != nil { panic(err) } // If the key is unique for each ciphertext, then it's ok to use a zero // IV. var iv [aes.BlockSize]byte stream := cipher.NewOFB(block, iv[:]) var out bytes.Buffer writer := &cipher.StreamWriter{S: stream, W: &out} // Copy the input to the output buffer, encrypting as we go. if _, err := io.Copy(writer, bReader); err != nil { panic(err) } // Note that this example is simplistic in that it omits any // authentication of the encrypted data. If you were actually to use // StreamReader in this manner, an attacker could flip arbitrary bits in // the decrypted result. fmt.Printf("%x\n", out.Bytes()) }
Package-Level Type Names (total 18, in which 6 are exported)
/* sort exporteds by: | */
AEAD is a cipher mode providing authenticated encryption with associated data. For a description of the methodology, see https://en.wikipedia.org/wiki/Authenticated_encryption NonceSize returns the size of the nonce that must be passed to Seal and Open. Open decrypts and authenticates ciphertext, authenticates the additional data and, if successful, appends the resulting plaintext to dst, returning the updated slice. The nonce must be NonceSize() bytes long and both it and the additional data must match the value passed to Seal. To reuse ciphertext's storage for the decrypted output, use ciphertext[:0] as dst. Otherwise, the remaining capacity of dst must not overlap plaintext. Even if the function fails, the contents of dst, up to its capacity, may be overwritten. Overhead returns the maximum difference between the lengths of a plaintext and its ciphertext. Seal encrypts and authenticates plaintext, authenticates the additional data and appends the result to dst, returning the updated slice. The nonce must be NonceSize() bytes long and unique for all time, for a given key. To reuse plaintext's storage for the encrypted output, use plaintext[:0] as dst. Otherwise, the remaining capacity of dst must not overlap plaintext. func NewGCM(cipher Block) (AEAD, error) func NewGCMWithNonceSize(cipher Block, size int) (AEAD, error) func NewGCMWithTagSize(cipher Block, tagSize int) (AEAD, error) func vendor/golang.org/x/crypto/chacha20poly1305.New(key []byte) (AEAD, error) func vendor/golang.org/x/crypto/chacha20poly1305.NewX(key []byte) (AEAD, error)
A Block represents an implementation of block cipher using a given key. It provides the capability to encrypt or decrypt individual blocks. The mode implementations extend that capability to streams of blocks. BlockSize returns the cipher's block size. Decrypt decrypts the first block in src into dst. Dst and src must overlap entirely or not at all. Encrypt encrypts the first block in src into dst. Dst and src must overlap entirely or not at all. func crypto/aes.NewCipher(key []byte) (Block, error) func crypto/des.NewCipher(key []byte) (Block, error) func crypto/des.NewTripleDESCipher(key []byte) (Block, error) func NewCBCDecrypter(b Block, iv []byte) BlockMode func NewCBCEncrypter(b Block, iv []byte) BlockMode func NewCFBDecrypter(block Block, iv []byte) Stream func NewCFBEncrypter(block Block, iv []byte) Stream func NewCTR(block Block, iv []byte) Stream func NewGCM(cipher Block) (AEAD, error) func NewGCMWithNonceSize(cipher Block, size int) (AEAD, error) func NewGCMWithTagSize(cipher Block, tagSize int) (AEAD, error) func NewOFB(b Block, iv []byte) Stream
A BlockMode represents a block cipher running in a block-based mode (CBC, ECB etc). BlockSize returns the mode's block size. CryptBlocks encrypts or decrypts a number of blocks. The length of src must be a multiple of the block size. Dst and src must overlap entirely or not at all. If len(dst) < len(src), CryptBlocks should panic. It is acceptable to pass a dst bigger than src, and in that case, CryptBlocks will only update dst[:len(src)] and will not touch the rest of dst. Multiple calls to CryptBlocks behave as if the concatenation of the src buffers was passed in a single run. That is, BlockMode maintains state and does not reset at each CryptBlocks call. func NewCBCDecrypter(b Block, iv []byte) BlockMode func NewCBCEncrypter(b Block, iv []byte) BlockMode
A Stream represents a stream cipher. XORKeyStream XORs each byte in the given slice with a byte from the cipher's key stream. Dst and src must overlap entirely or not at all. If len(dst) < len(src), XORKeyStream should panic. It is acceptable to pass a dst bigger than src, and in that case, XORKeyStream will only update dst[:len(src)] and will not touch the rest of dst. Multiple calls to XORKeyStream behave as if the concatenation of the src buffers was passed in a single run. That is, Stream maintains state and does not reset at each XORKeyStream call. *crypto/rc4.Cipher *vendor/golang.org/x/crypto/chacha20.Cipher func NewCFBDecrypter(block Block, iv []byte) Stream func NewCFBEncrypter(block Block, iv []byte) Stream func NewCTR(block Block, iv []byte) Stream func NewOFB(b Block, iv []byte) Stream
StreamReader wraps a Stream into an io.Reader. It calls XORKeyStream to process each slice of data which passes through. R io.Reader S Stream ( T) Read(dst []byte) (n int, err error) T : io.Reader
StreamWriter wraps a Stream into an io.Writer. It calls XORKeyStream to process each slice of data which passes through. If any Write call returns short then the StreamWriter is out of sync and must be discarded. A StreamWriter has no internal buffering; Close does not need to be called to flush write data. // unused S Stream W io.Writer Close closes the underlying Writer and returns its Close return value, if the Writer is also an io.Closer. Otherwise it returns nil. ( T) Write(src []byte) (n int, err error) T : io.Closer T : io.WriteCloser T : io.Writer
Package-Level Functions (total 21, in which 9 are exported)
NewCBCDecrypter returns a BlockMode which decrypts in cipher block chaining mode, using the given Block. The length of iv must be the same as the Block's block size and must match the iv used to encrypt the data.
NewCBCEncrypter returns a BlockMode which encrypts in cipher block chaining mode, using the given Block. The length of iv must be the same as the Block's block size.
NewCFBDecrypter returns a Stream which decrypts with cipher feedback mode, using the given Block. The iv must be the same length as the Block's block size.
NewCFBEncrypter returns a Stream which encrypts with cipher feedback mode, using the given Block. The iv must be the same length as the Block's block size.
NewCTR returns a Stream which encrypts/decrypts using the given Block in counter mode. The length of iv must be the same as the Block's block size.
NewGCM returns the given 128-bit, block cipher wrapped in Galois Counter Mode with the standard nonce length. In general, the GHASH operation performed by this implementation of GCM is not constant-time. An exception is when the underlying Block was created by aes.NewCipher on systems with hardware support for AES. See the crypto/aes package documentation for details.
NewGCMWithNonceSize returns the given 128-bit, block cipher wrapped in Galois Counter Mode, which accepts nonces of the given length. The length must not be zero. Only use this function if you require compatibility with an existing cryptosystem that uses non-standard nonce lengths. All other users should use NewGCM, which is faster and more resistant to misuse.
NewGCMWithTagSize returns the given 128-bit, block cipher wrapped in Galois Counter Mode, which generates tags with the given length. Tag sizes between 12 and 16 bytes are allowed. Only use this function if you require compatibility with an existing cryptosystem that uses non-standard tag lengths. All other users should use NewGCM, which is more resistant to misuse.
NewOFB returns a Stream that encrypts or decrypts using the block cipher b in output feedback mode. The initialization vector iv's length must be equal to b's block size.
Package-Level Variables (total 2, neither is exported)
Package-Level Constants (total 5, none are exported)