blob: 79eb00acf8f46035f3ac2e51396cb2a5893cfc57 [file] [log] [blame]
/**
* Copyright 2017 Google Inc.
*
* 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.
*
**************************************************************************
*/
#import <Foundation/Foundation.h>
NS_ASSUME_NONNULL_BEGIN
/**
* The protocol for hybrid encryption.
*
* Implementations of this protocol are secure against adaptive chosen ciphertext attacks. In
* addition to @c plaintext the encryption takes an extra parameter @c contextInfo, which usually is
* public data implicit from the context, but should be bound to the resulting ciphertext: upon
* decryption the ciphertext allows for checking the integrity of @c contextInfo (but there are no
* guarantees with regard to secrecy or authenticity of @c contextInfo).
*
* WARNING: Hybrid Encryption does not provide authenticity, that is the recipient of an encrypted
* message does not know the identity of the sender. Similar to general public-key encryption
* schemes the security goal of Hybrid Encryption is to provide privacy only. In other words,
* Hybrid Encryption is secure if and only if the recipient can accept anonymous messages or can
* rely on other mechanisms to authenticate the sender.
*
* @c contextInfo can be empty or nil, but to ensure the correct decryption of the resulting
* ciphertext the same value must be provided for the decryption operation.
*
* A concrete instantiation of this interface can implement the binding of @c contextInfo to the
* ciphertext in various ways, for example:
*
* - Use @c contextInfo as "associated data"-input for the employed AEAD symmetric encryption
* (https://tools.ietf.org/html/rfc5116).
* - Use @c contextInfo as "CtxInfo"-input for HKDF (if the implementation uses HKDF as key
* derivation function: https://tools.ietf.org/html/rfc5869).
*/
@protocol TINKHybridEncrypt <NSObject>
/* Encrypts @c plaintext binding @c contextInfo to the resulting ciphertext. */
- (nullable NSData *)encrypt:(NSData *)plaintext
withContextInfo:(nullable NSData *)contextInfo
error:(NSError **)error;
@end
NS_ASSUME_NONNULL_END