Package com.google.crypto.tink

Interface HybridEncrypt

All Known Implementing Classes:

EciesAeadHkdfHybridEncrypt, HpkeEncrypt, LegacyFullHybridEncrypt, RsaKemHybridEncrypt

public interface HybridEncrypt

Interface for hybrid encryption.

Hybrid Encryption combines the efficiency of symmetric encryption with the convenience of public-key encryption: to encrypt a message a fresh symmetric key is generated and used to encrypt the actual plaintext data, while the recipient’s public key is used to encrypt the symmetric key only, and the final ciphertext consists of the symmetric ciphertext and the encrypted symmetric key.

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.

Security guarantees

The functionality of Hybrid Encryption is represented as a pair of primitives (interfaces): HybridEncrypt for encryption of data, and HybridDecrypt for decryption. Implementations of these interfaces are secure against adaptive chosen ciphertext attacks. In addition to plaintext the encryption takes an extra parameter contextInfo, which usually is public data implicit from the context, but should be bound to the resulting ciphertext, i.e. the ciphertext allows for checking the integrity of contextInfo (but there are no guarantees wrt. the secrecy or authenticity of contextInfo).

contextInfo can be empty or null, but to ensure the correct decryption of a ciphertext the same value must be provided for the decryption operation as was used during encryption (cf. HybridEncrypt).

A concrete instantiation of this interface can implement the binding of contextInfo to the ciphertext in various ways, for example:

• use contextInfo as "associated data"-input for the employed AEAD symmetric encryption (cf. https://tools.ietf.org/html/rfc5116).
• use contextInfo as "CtxInfo"-input for HKDF (if the implementation uses HKDF as key derivation function, cf. https://tools.ietf.org/html/rfc5869).

Since:

1.0.0

Method Summary

Modifier and Type	Method	Description
byte[]	encrypt(byte[] plaintext, byte[] contextInfo)	Encryption operation: encrypts plaintext binding contextInfo to the resulting ciphertext.

Method Detail

encrypt

byte[] encrypt(byte[] plaintext,
               byte[] contextInfo)
        throws java.security.GeneralSecurityException

Encryption operation: encrypts plaintext binding contextInfo to the resulting ciphertext.

Returns:

resulting ciphertext

Throws:

java.security.GeneralSecurityException