General purpose Python encrypted file-like object that facilitates random access IO. Uses AES encryption in CTR mode. Can be used with modules such as tarfile, zipfile, lzma, pickle, json and others that accept a file-like object as an alternative to a path. Supports binary IO modes only.

Cryptfile uses its own file format by writing and encrypting data across blocks with each block using and storing a unique CTR nonce value. Safe random access is achieved by reencrypting any block that receives a write with a new random nonce value.

Also includes CryptFileStream which is an encrypted file-like object that facilitiates stream IO with a single nonce.

Examples

import cryptfile

with cryptfile.open('data.bin', 'wb+', aes_key=b'256 bit key', block_num=5000) as f:
    f.write(b'Hello, World!')
    f.seek(0)
    print(f.read())
     
Result:
b'Hello, World!'

Documentation

cryptfile.open(file, mode, aes_key=None, block_num=10000)

Returns a CryptFile object for a specified file.

• file can either be a string containing a valid path, or a file-like object. When using a file-like object for writing, the object's IO mode must also support reading.
• Supported mode values are: wb, wb+, rb, rb+, ab, ab+.
• 256 bit binary aes_key is used for en/decryption, or if none is provided for a new file, a random key is generated and is retrievable with the .aeskey property.
• block_num sets the number of 16 byte AES blocks per cryptfile block for new files. Each cryptfile block stores its own 8 byte nonce value, and is re-written in whole if any part of the block is altered. Larger block_num values optimize for more sequential IO, whereas smaller values optimize for smaller random IO that jumps around the file. This argument is not needed for opening existing files.

cryptfilestream.open(file, mode, aes_key=None)

Returns a CryptFileStream object for a specified file.

• file can either be a string containing a valid path, or a file-like object.
• Supported mode values are: wb, rb.
• 256 bit binary aes_key is used for en/decryption, or if none is provided for a new file, a random key is generated and is retrievable with the .aeskey property.

Dependencies

PyCryptodome for AES encryption

Installation

pip install cryptfile