basic_encryption.py

# Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
# SPDX-License-Identifier: Apache-2.0
"""Example showing how to encrypt and decrypt a value in memory."""
import aws_encryption_sdk


def run(aws_kms_cmk, source_plaintext, botocore_session=None):
    """Encrypts and then decrypts a string under a KMS customer master key (CMK).

    :param str aws_kms_cmk: Amazon Resource Name (ARN) of the AWS KMS CMK
    :param bytes source_plaintext: Data to encrypt
    :param botocore_session: existing botocore session instance
    :type botocore_session: botocore.session.Session
    """
    # Create a KMS master key provider
    kms_kwargs = dict(key_ids=[aws_kms_cmk])
    if botocore_session is not None:
        kms_kwargs["botocore_session"] = botocore_session
    master_key_provider = aws_encryption_sdk.KMSMasterKeyProvider(**kms_kwargs)

    # Encrypt the plaintext source data
    ciphertext, encryptor_header = aws_encryption_sdk.encrypt(source=source_plaintext, key_provider=master_key_provider)

    # Decrypt the ciphertext
    cycled_plaintext, decrypted_header = aws_encryption_sdk.decrypt(source=ciphertext, key_provider=master_key_provider)

    # Verify that the "cycled" (encrypted, then decrypted) plaintext is identical to the source plaintext
    assert cycled_plaintext == source_plaintext

    # Verify that the encryption context used in the decrypt operation includes all key pairs from
    # the encrypt operation. (The SDK can add pairs, so don't require an exact match.)
    #
    # In production, always use a meaningful encryption context. In this sample, we omit the
    # encryption context (no key pairs).
    assert all(
        pair in decrypted_header.encryption_context.items() for pair in encryptor_header.encryption_context.items()
    )