2.1. Asymmetric Encryption

Asymmetric encryption is implemented using the RSA cryptosystem. These types and functions are designed for encryption purposes only (that is, not digital signatures); if you need to digitally sign data, use Digital Signatures.

Warning

The maximum amount of data that can be encrypted in a single crypto.AsymmetricEncrypt operation is small (around 130 bytes).

2.1.1. Types

class AsymmetricEncryptKey

The RSA public key for public-key encryption with RSA.

class AsymmetricDecryptKey

The RSA private key, used for RSA decryption.

2.1.2. Functions

crypto.AsymmetricKeyGen() → Tuple[AsymmetricEncryptKey, AsymmetricDecryptKey]

Generates a public-key pair for asymmetric encryption purposes.

Returns:

A tuple corresponding to a AsymmetricEncryptKey and AsymmetricDecryptKey pair

Return type:

Tuple[AsymmetricEncryptKey, AsymmetricDecryptKey]

Example usage:

# Returns a tuple, so assign return values to two variables:
public_key, private_key = crypto.AsymmetricKeyGen()

crypto.AsymmetricEncrypt(key: AsymmetricEncryptKey, plaintext: bytes) → bytes

Uses the public key key to encrypt plaintext. This function, on its own, is \(\textsf{IND-CPA}\) secure.

Parameters:

• key (AsymmetricEncryptKey) – The public key

• plaintext (bytes) – The plaintext to encrypt

Returns:

The encrypted ciphertext

Return type:

bytes

Raises:

ValueError – if message was too long

crypto.AsymmetricDecrypt(key: AsymmetricDecryptKey, ciphertext: bytes) → bytes

Uses the private key key to decrypt ciphertext.

Parameters:

• key (AsymmetricDecryptKey) – The private key

• ciphertext (bytes) – The ciphertext to decrypt

Returns:

The decrypted plaintext

Return type:

bytes

2.1.3. Class Methods

Note

You probably don’t have to worry about the methods below if you’re just thinking about the design, but you’ll probably need to use them once you start implementing your client application.

These class methods are for the purposes of serialization (see Serialization API). Also, see Key Serialization Example for example usage.

classmethod crypto.AsymmetricEncryptKey.from_bytes(b: bytes) → AsymmetricEncryptKey

Converts a serialized bytes representation of a AsymmetricEncryptKey to an actual Python instance of AsymmetricEncryptKey.

Returns:

The deserialized AsymmetricEncryptKey instance

Return type:

AsymmetricEncryptKey

Raises:

ValueError – if b was not a valid encoding of a AsymmetricEncryptKey instance

classmethod crypto.AsymmetricDecryptKey.from_bytes(b: bytes) → AsymmetricDecryptKey

Converts a serialized bytes representation of a AsymmetricDecryptKey to an actual Python instance of AsymmetricDecryptKey.

Returns:

The deserialized AsymmetricDecryptKey instance

Return type:

AsymmetricDecryptKey

Raises:

ValueError – if b was not a valid encoding of a AsymmetricDecryptKey instance