go/tink/deterministic_aead.go

// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
////////////////////////////////////////////////////////////////////////////////

package tink

/*
DeterministicAEAD is the interface for deterministic authenticated encryption with associated data.

Warning:
Unlike AEAD, implementations of this interface are not semantically secure, because
encrypting the same plaintex always yields the same ciphertext.

Security guarantees:
Implementations of this interface provide 128-bit security level against multi-user attacks
with up to 2^32 keys. That means if an adversary obtains 2^32 ciphertexts of the same message
encrypted under 2^32 keys, they need to do 2^128 computations to obtain a single key.

Encryption with associated data ensures authenticity (who the sender is) and integrity (the
data has not been tampered with) of that data, but not its secrecy.

References:
https://tools.ietf.org/html/rfc5116
https://tools.ietf.org/html/rfc5297#section-1.3
*/
type DeterministicAEAD interface {
	// EncryptDeterministically deterministically encrypts plaintext with additionalData as
	// additional authenticated data. The resulting ciphertext allows for checking
	// authenticity and integrity of additional data additionalData,
	// but there are no guarantees wrt. secrecy of that data.
	EncryptDeterministically(plaintext, additionalData []byte) ([]byte, error)

	// DecryptDeterministically deterministically decrypts ciphertext with additionalData as
	// additional authenticated data. The decryption verifies the authenticity and integrity
	// of the additional data, but there are no guarantees wrt. secrecy of that data.
	DecryptDeterministically(ciphertext, additionalData []byte) ([]byte, error)
}