subtle

Documentation

Overview

Package subtle provides subtle implementations of the DeterministicAEAD primitive.

Index

• Constants
• type AESSIV
  • func NewAESSIV(key []byte) (*AESSIV, error)
  • func (asc *AESSIV) DecryptDeterministically(ciphertext, associatedData []byte) ([]byte, error)
  • func (asc *AESSIV) EncryptDeterministically(plaintext, associatedData []byte) ([]byte, error)

Constants

const (
	// AESSIVKeySize is the key size in bytes.
	AESSIVKeySize = 64
)

Types

type AESSIV

type AESSIV struct {
	K1     []byte
	K2     []byte
	CmacK1 []byte
	CmacK2 []byte
	Cipher cipher.Block
}

AESSIV is an implementation of AES-SIV-CMAC as defined in https://tools.ietf.org/html/rfc5297.

AESSIV implements a deterministic encryption with associated data (i.e. the DeterministicAEAD interface). Hence the implementation below is restricted to one AD component.

Security Note:

Chatterjee, Menezes and Sarkar analyze AES-SIV in Section 5.1 of https://www.math.uwaterloo.ca/~ajmeneze/publications/tightness.pdf

Their analysis shows that AES-SIV is susceptible to an attack in a multi-user setting. Concretely, if an attacker knows the encryption of a message m encrypted and authenticated with k different keys, then it is possible to find one of the MAC keys in time 2^b / k where b is the size of the MAC key. A consequence of this attack is that 128-bit MAC keys give unsufficient security. Since 192-bit AES keys are not supported by tink for voodoo reasons and RFC 5297 only supports same size encryption and MAC keys this implies that keys must be 64 bytes (2*256 bits) long.

func NewAESSIV

func NewAESSIV(key []byte) (*AESSIV, error)

NewAESSIV returns an AESSIV instance.

func (*AESSIV) DecryptDeterministically

func (asc *AESSIV) DecryptDeterministically(ciphertext, associatedData []byte) ([]byte, error)

DecryptDeterministically deterministically decrypts ciphertext with associatedData.

func (*AESSIV) EncryptDeterministically

func (asc *AESSIV) EncryptDeterministically(plaintext, associatedData []byte) ([]byte, error)

EncryptDeterministically deterministically encrypts plaintext with associatedData.