peewee_encrypted_field 0.0.2

Field with encryption/decryption on save/read for use in Peewee ORM models

Encrypted field for Peewee ORM models to save data in DB in encrypted form.

Data stored in DataBase as Fernet tokens. After you define an encryption key all cryptography will be performed transparently for your application.

Uses simple fernet implementation https://github.com/heroku/fernet-py

Idea caught from SQLAlchemy’s EncryptedType.

Contents

• Implementation Details

• Features

• Installation

• Usage

• Key Derivation Example

Implementation Details

A fernet-py package can use Pycrypto or M2Crypto as backend (details). Same belongs to this module due to its dependency from fernet-py. Note that pip uses Pycrypto as a default dependency when install fernet-py. Length of entire key is 32 bytes, 16 bytes per both signing and encryption keys, as stated in specification.

Features

You have to set key as a property of appropriate EncryptedField. You need to set this property once per Model per Model ‘s Field. If you attempt to set key property for a Field whose key already has been set, exception EncryptedField.KeyAlreadyExists will be raised. To change the key on the fly you have to explictly perform del SomeEncryptedField.key and then set this property to desired value again.

Installation

pip install peewee_encrypted_field

or, if you downloaded source,

python setup.py install

Usage

At first, import module

from peewee import *
from peewee_encrypted_field import EncryptedField

Then, define the model with EncryptedField

class SecureTable(BaseModel):
    sensitive_data = EncryptedField()

    class Meta:
        db_table = 'SecureTable'

After, configure field’s encryption key

SecureTable.sensitive_data.key = key_derivation_fn()  # a hypotetical key derivation
                                                      # function returning 32 byte key

Finally, save and retrieve data in a Peewee’s usual manner

new_secret = SecureTable(sensitive_data='My New BIG Secret')
new_secret.save()

Key Derivation Example

Example Key Derivation Function baded on Pycrypto module.

Please take look at this Gist - it can contain more actual version of code below.

from binascii import unhexlify
from functools import partial
from Crypto.Protocol import KDF
from Crypto.Hash import SHA512, HMAC

_SALT = unhexlify('48B755AB80CD1C3DA61182D3DCD2E3A2CA869B783618FF6551FB4B0CDC3B8066')  # some salt
_KEY_LENGTH = 32

key_derivation_fn = partial(
    KDF.PBKDF2,
    salt=_SALT,
    dkLen=_KEY_LENGTH,
    count=5000,
    prf=lambda p,s: HMAC.new(p,s,SHA512).digest()
)

# KDF usage
SecureTable.sensitive_data.key = key_derivation_fn(text_password)