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The AWS Encryption SDK for Python provides a fully compliant, native Python implementation of the AWS Encryption SDK.

The latest full documentation can be found at Read the Docs.

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Getting Started

Required Prerequisites

  • Python 2.7+ or 3.4+
  • cryptography >= 1.8.1
  • boto3
  • attrs



If you have not already installed cryptography, you might need to install additional prerequisites as detailed in the cryptography installation guide for your operating system.

$ pip install aws-encryption-sdk


There are four main concepts that you need to understand to use this library:

Cryptographic Materials Managers

Cryptographic materials managers (CMMs) are resources that collect cryptographic materials and prepare them for use by the Encryption SDK core logic.

An example of a CMM is the default CMM, which is automatically generated anywhere a caller provides a master key provider. The default CMM collects encrypted data keys from all master keys referenced by the master key provider.

An example of a more advanced CMM is the caching CMM, which caches cryptographic materials provided by another CMM.

Master Key Providers

Master key providers are resources that provide master keys. An example of a master key provider is AWS KMS.

To encrypt data in this client, a MasterKeyProvider object must contain at least one MasterKey object.

MasterKeyProvider objects can also contain other MasterKeyProvider objects.

Master Keys

Master keys generate, encrypt, and decrypt data keys. An example of a master key is a KMS customer master key (CMK).

Data Keys

Data keys are the encryption keys that are used to encrypt your data. If your algorithm suite uses a key derivation function, the data key is used to generate the key that directly encrypts the data.


To use this client, you (the caller) must provide an instance of either a master key provider or a CMM. The examples in this readme use the KMSMasterKeyProvider class.


Because the KMSMasterKeyProvider uses the boto3 SDK to interact with AWS KMS, it requires AWS Credentials. To provide these credentials, use the standard means by which boto3 locates credentials or provide a pre-existing instance of a botocore session to the KMSMasterKeyProvider. This latter option can be useful if you have an alternate way to store your AWS credentials or you want to reuse an existing instance of a botocore session in order to decrease startup costs.

import aws_encryption_sdk
import botocore.session

kms_key_provider = aws_encryption_sdk.KMSMasterKeyProvider()

existing_botocore_session = botocore.session.Session()
kms_key_provider = aws_encryption_sdk.KMSMasterKeyProvider(botocore_session=existing_botocore_session)

You can pre-load the KMSMasterKeyProvider with one or more CMKs. To encrypt data, you must configure the KMSMasterKeyProvider with as least one CMK. If you configure the the KMSMasterKeyProvider with multiple CMKs, the final message will include a copy of the data key encrypted by each configured CMK.

import aws_encryption_sdk

kms_key_provider = aws_encryption_sdk.KMSMasterKeyProvider(key_ids=[

You can add CMKs from multiple regions to the KMSMasterKeyProvider.

import aws_encryption_sdk

kms_key_provider = aws_encryption_sdk.KMSMasterKeyProvider(key_ids=[

Encryption and Decryption

After you create an instance of a MasterKeyProvider, you can use either of the two high-level encrypt/decrypt functions to encrypt and decrypt your data.

import aws_encryption_sdk

kms_key_provider = aws_encryption_sdk.KMSMasterKeyProvider(key_ids=[
my_plaintext = b'This is some super secret data!  Yup, sure is!'

my_ciphertext, encryptor_header = aws_encryption_sdk.encrypt(

decrypted_plaintext, decryptor_header = aws_encryption_sdk.decrypt(

assert my_plaintext == decrypted_plaintext
assert encryptor_header.encryption_context == decryptor_header.encryption_context

You can provide an encryption context: a form of additional authenticating information.

import aws_encryption_sdk

kms_key_provider = aws_encryption_sdk.KMSMasterKeyProvider(key_ids=[
my_plaintext = b'This is some super secret data!  Yup, sure is!'

my_ciphertext, encryptor_header = aws_encryption_sdk.encrypt(
        'not really': 'a secret',
        'but adds': 'some authentication'

decrypted_plaintext, decryptor_header = aws_encryption_sdk.decrypt(

assert my_plaintext == decrypted_plaintext
assert encryptor_header.encryption_context == decryptor_header.encryption_context


If you are handling large files or simply do not want to put the entire plaintext or ciphertext in memory at once, you can use this library’s streaming clients directly. The streaming clients are file-like objects, and behave exactly as you would expect a Python file object to behave, offering context manager and iteration support.

import aws_encryption_sdk
import filecmp

kms_key_provider = aws_encryption_sdk.KMSMasterKeyProvider(key_ids=[
plaintext_filename = 'my-secret-data.dat'
ciphertext_filename = 'my-encrypted-data.ct'

with open(plaintext_filename, 'rb') as pt_file, open(ciphertext_filename, 'wb') as ct_file:
    ) as encryptor:
        for chunk in encryptor:

new_plaintext_filename = 'my-decrypted-data.dat'

with open(ciphertext_filename, 'rb') as ct_file, open(new_plaintext_filename, 'wb') as pt_file:
    ) as decryptor:
        for chunk in decryptor:

assert filecmp.cmp(plaintext_filename, new_plaintext_filename)
assert encryptor.header.encryption_context == decryptor.header.encryption_context

Performance Considerations

Adjusting the frame size can significantly improve the performance of encrypt/decrypt operations with this library.

Processing each frame in a framed message involves a certain amount of overhead. If you are encrypting a large file, increasing the frame size can offer potentially significant performance gains. We recommend that you tune these values to your use-case in order to obtain peak performance.


aws_encryption_sdk High level AWS Encryption SDK client functions.
aws_encryption_sdk.exceptions Contains exception classes for AWS Encryption SDK.
aws_encryption_sdk.identifiers AWS Encryption SDK native data structures for defining implementation-specific characteristics.
aws_encryption_sdk.caches Common functions and structures for use in cryptographic materials caches.
aws_encryption_sdk.caches.base Base class interface for caches for use with caching crypto material managers.
aws_encryption_sdk.caches.local Local, in-memory, LRU, cryptographic materials cache for use with caching cryptographic materials providers.
aws_encryption_sdk.caches.null Null cache: a cache which does not cache.
aws_encryption_sdk.key_providers.base Base class interface for Master Key Providers.
aws_encryption_sdk.key_providers.kms Master Key Providers for use with AWS KMS
aws_encryption_sdk.key_providers.raw Resources required for Raw Master Keys.
aws_encryption_sdk.materials_managers Primitive structures for use when interacting with crypto material managers.
aws_encryption_sdk.materials_managers.base Base class interface for crypto material managers.
aws_encryption_sdk.materials_managers.caching Caching crypto material manager.
aws_encryption_sdk.materials_managers.default Default crypto material manager class.
aws_encryption_sdk.streaming_client High level AWS Encryption SDK client for streaming objects.
aws_encryption_sdk.structures Public data structures for aws_encryption_sdk.
aws_encryption_sdk.internal Internal Implementation Details
aws_encryption_sdk.internal.crypto.authentication Contains authentication primitives.
aws_encryption_sdk.internal.crypto.data_keys Contains data key helper functions.
aws_encryption_sdk.internal.crypto.elliptic_curve Contains elliptic curve functionality.
aws_encryption_sdk.internal.crypto.encryption Contains encryption primitives and helper functions.
aws_encryption_sdk.internal.crypto.iv Helper functions used for generating deterministic initialization vectors (IVs).
aws_encryption_sdk.internal.crypto.wrapping_keys Contains wrapping key primitives.
aws_encryption_sdk.internal.defaults Default values for AWS Encryption SDK.
aws_encryption_sdk.internal.formatting Formatting functions for aws_encryption_sdk.
aws_encryption_sdk.internal.formatting.deserialize Components for handling AWS Encryption SDK message deserialization.
aws_encryption_sdk.internal.formatting.encryption_context Components for handling serialization and deserialization of encryption context data in AWS Encryption SDK messages.
aws_encryption_sdk.internal.formatting.serialize Components for handling AWS Encryption SDK message serialization.
aws_encryption_sdk.internal.str_ops Helper functions for consistently obtaining str and bytes objects in both Python2 and Python3.
aws_encryption_sdk.internal.structures Public data structures for aws_encryption_sdk.
aws_encryption_sdk.internal.utils Helper utility functions for AWS Encryption SDK.


1.4.1 – 2019-09-20


  • Fix region configuration override in botocore sessions. #190 #193


  • Caching CMM must require that max age configuration value is greater than 0. #147 #172

1.4.0 – 2019-05-23


  • Remove dependence on all source_stream APIs except for read(). #103
Potentially Backwards Incompatible
  • Encryption streams no longer close the source_stream when they themselves close. If you are using context managers for all of your stream handling, this change will not affect you. However, if you have been relying on the StreamDecryptor or StreamEncryptor to close your source_stream for you, you will now need to close those streams yourself.
  • StreamDecryptor.body_start and StreamDecryptor.body_end, deprecated in a prior release, have now been removed.


  • Move all remaining unittest tests to pytest. #99


  • Fix MasterKeyprovider.decrypt_data_key_from_list error handling. #150

1.3.8 – 2018-11-15


  • Remove debug logging that may contain input data when encrypting non-default unframed messages. #105


  • Add support to remove clients from KMSMasterKeyProvider client cache if they fail to connect to endpoint. #86
  • Add support for SHA384 and SHA512 for use with RSA OAEP wrapping algorithms. #56
  • Fix streaming_client classes to properly interpret short reads in source streams. #24

1.3.7 – 2018-09-20


  • Fix KMSMasterKeyProvider to determine the default region before trying to create the requested master keys. #83

1.3.6 – 2018-09-04


  • StreamEncryptor and StreamDecryptor should always report as readable if they are open. #73
  • Allow duck-typing of source streams. #75

1.3.5 – 2018-08-01

  • Move the aws-encryption-sdk-python repository from awslabs to aws.

1.3.4 – 2018-04-12


  • AWS KMS master key/provider user agent extension fixed. #47


  • New minimum pytest version 3.3.1 to avoid bugs in 3.3.0 #32
  • New minimum attrs version 17.4.0 to allow use of converter rather than convert #39
  • Algorithm Suites are modeled as collections of sub-suites now #36
  • Selecting test suites is more sane now, with pytest markers. #41

1.3.3 – 2017-12-05


  • Remove use of attrs functionality deprecated in 17.3.0 #29


1.3.2 – 2017-09-28

  • Addressed issue #13 to properly handle non-seekable source streams.

1.3.1 – 2017-09-12


  • Moved source into src.
  • Moved examples into examples.
  • Broke out internal.crypto into smaller, feature-oriented, modules.


  • Added tox configuration to support automation and development tooling.
  • Added pylint, flake8, and doc8 configuration to enforce style rules.


  • Updated internal.crypto.authentication.Verifier to use Prehashed.
  • Addressed docstring issue #7.
  • Addressed docstring issue #8.
  • Addressed logging issue #10.
  • Addressed assorted linting issues to bring source, tests, examples, and docs up to configured linting standards.

1.3.0 – 2017-08-04


  • Added cryptographic materials managers as a concept
  • Added data key caching
  • Moved to deterministic IV generation


  • Added changelog
  • Fixed attrs usage to provide consistent behavior with 16.3.0 and 17.x
  • Fixed performance bug which caused KDF calculations to be performed too frequently
  • Removed line_length as a configurable parameter of EncryptingStream and DecryptingStream objects to simplify class APIs after it was found in further testing to have no measurable impact on performance
  • Added deterministic length eliptic curve signature generation
  • Added support for calculating ciphertext message length from header
  • Migrated README from md to rst

1.2.2 – 2017-05-23

1.2.0 – 2017-03-21

  • Initial public release