AES cipher is a library to encrypt/decrypt using AES256-CBC. It is possible to encrypt/decrypt both files and raw data (string or bytes).
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A master key and IV are derived from the given password and (optionally) salt using a key derivation function. The key derivation function can be chosen among the provided ones:
- PBKDF2-SHA512
- Scrypt
Alternatively, it can also be customized by the user by simply implementing the
IKeyDerivator
interface.
Salt is randomly generated (16-byte long) if not specified. -
A random key and IV are generated and used to encrypt the actual data. In this way, if the same file is encrypted with the same password multiple times, the encrypted file will always be different.
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The random key and IV are encrypted with the master key and IV
-
HMAC-SHA256 of the encrypted key/IV and file data is computed to ensure integrity, using the master key as key
It is possible to specify either a single password or a list of passwords. In the last case, the file will be encrypted multiple times with a different password and salt each time.
The package requires Python >= 3.7.
To install it:
-
Using setuptools:
python setup.py install
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Using pip:
pip install aes_cipher
Install develop dependencies:
pip install -r requirements-dev.txt
To run tests:
python -m unittest discover
To run tests with coverage:
coverage run -m unittest discover
coverage report
Pbkdf2Sha512
class: derive keys using PBKDF2-SHA512 algorithm
Pbkdf2Sha512(itr_num)
: construct the classitr_num
: iterations number
For default values, the Pbkdf2Sha512Default
class instance can be used:
Pbkdf2Sha512Default = Pbkdf2Sha512(512 * 1024)
Scrypt
class: derive keys using Scrypt algorithm
Scrypt(n, p, r)
: construct the classn
: CPU/Memory cost parameterp
: block size parameterr
: parallelization parameter
For default values, the ScryptDefault
class instance can be used:
ScryptDefault = Scrypt(16384, 8, 8)
To add a custom key derivation function, the IKeyDerivator
interface shall be implemented:
class IKeyDerivator(ABC):
@abstractmethod
def DeriveKey(self,
password: Union[str, bytes],
salt: Union[str, bytes]) -> bytes:
pass
The only requirement is that the output of the DeriveKey
method is at least 48-byte long.
A constructor can be added to customize the algorithm.
DataEncrypter
class: encrypt bytes or string data
DataEncrypter(key_derivator)
: construct the classkey_derivator
: key derivator to be used for master key and IV generation, it shall be an instance of theIKeyDerivator
interface. Default value:Pbkdf2Sha512Default
.
DataEncrypter.Encrypt(data, passwords [, salts])
: encrypt data with the specified passwords and saltsdata
: input data (string or bytes)passwords
: list of passwords (list of strings)salts
(optional): list of salts (list of strings). The number of salts shall be the same of the passwords. If not specified, salts will be randomly generated (16-byte long).
DataEncrypter.GetEncryptedData()
: get encrypted data (bytes)
FileEncrypter
class: encrypt a file
FileEncrypter(key_derivator)
: construct the classkey_derivator
: seeDataEncrypter
constructor
FileEncrypter.Encrypt(file_in, passwords [, salts])
: encrypt file with the specified passwords and saltsfile_in
: input filepasswords
: seeDataEncrypter.Encrypt
salts
: seeDataEncrypter.Encrypt
FileEncrypter.GetEncryptedData()
: get encrypted data (bytes)FileEncrypter.SaveTo(file_out)
: save to filefile_out
: output file to be saved
DataDecrypter
class: decrypt bytes or string data
DataDecrypter(key_derivator)
: construct the classkey_derivator
: key derivator to be used for master key and IV generation, it shall be an instance of theIKeyDerivator
interface. Default value:Pbkdf2Sha512Default
.
DataDecrypter.Decrypt(data, passwords)
: decrypt data with the specified passwordsdata
: input data (string or bytes)passwords
: seeDataEncrypter.Encrypt
DataDecrypter.GetDecryptedData()
: get decrypted data (bytes)
FileDecrypter
class: decrypt a file
FileDecrypter(key_derivator)
: construct the classkey_derivator
: seeDataDecrypter
constructor
FileDecrypter.Decrypt(file_in, passwords)
file_in
: input filepasswords
: seeDataDecrypter.Decrypt
FileDecrypter.GetDecryptedData()
: get decrypted data (bytes)FileDecrypter.SaveTo(file_out)
: save to filefile_out
: output file to be saved
Data encryption with single password and random salt, using PBKDF2-SHA512 algorithm with default values:
data_encrypter = DataEncrypter(Pbkdf2Sha512Default)
data_encrypter.Encrypt(data, "test_pwd")
enc_data = data_encrypter.GetEncryptedData()
Data encryption with single password and custom salt, using PBKDF2-SHA512 algorithm with custom values:
data_encrypter = DataEncrypter(
Pbkdf2Sha512(1024 * 1024)
)
data_encrypter.Encrypt(data, ["test_pwd"], ["test_salt"])
enc_data = data_encrypter.GetEncryptedData()
Data encryption with multiple passwords and custom salts, using Scrypt algorithm with default values:
data_encrypter = DataEncrypter(ScryptDefault)
data_encrypter.Encrypt(data, ["test_pwd_1", "test_pwd_2"], ["test_salt_1", "test_salt_2"])
enc_data = data_encrypter.GetEncryptedData()
Data decryption with single password and random salt:
data_decrypter = DataDecrypter()
data_decrypter.Decrypt(data, ["test_pwd"])
dec_data = data_decrypter.GetDecryptedData()
Data decryption with multiple passwords and custom salts:
data_decrypter = DataDecrypter()
data_decrypter.Decrypt(data, ["test_pwd_1", "test_pwd_2"], ["test_salt_1", "test_salt_2"])
dec_data = data_decrypter.GetDecryptedData()
File encryption with single password and random salt:
file_encrypter = FileEncrypter()
file_encrypter.Encrypt(file_in, "test_pwd")
file_encrypter.SaveTo(file_out)
Enable logging:
data_encrypter = DataEncrypter()
data_encrypter.Logger().SetLevel(logging.INFO)
data_decrypter = DataDecrypter()
data_decrypter.Logger().SetLevel(logging.INFO)
A sample application based on the library using the PBKDF2-SHA512 algorithm can be found in the app folder.
Basic usage:
python aes_cipher_app.py -m <enc:dec> -p <password1,password2,...> -i <input_files_or_folder> -o <output_folder> [-s <salt1,salt2,...>] [-t <itr_num>] [-v] [-h]
Parameters description:
Short name | Long name | Description |
---|---|---|
-m |
--mode |
Operational mode: enc for encrypting, dec for decrypting |
-p |
--password |
Password used for encrypting/decrypting. It can be a single password or a list of passwords separated by a comma |
-i |
--input |
Input to be encrypted/decrypted. It can be a single file, a list of files separated by a comma or a folder (in this case all files in the folder will be encrypted/decrypted) |
-o |
--output |
Output folder where the encrypted/decrypted files will be saved |
-s |
--salt |
Optional: custom salts for master key and IV derivation, random if not specified` |
-t |
--iteration |
Optional: number of iteration for the PBKDF2-SHA512 algorithm, default value: 524288 |
-v |
--verbose |
Optional: enable verbose mode |
-h |
--help |
Optional: print usage and exit |
NOTE: the password shall not contain spaces or commas (in this case it will be interpreted as multiple passwords)
Examples:
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Encrypt a file one time with the given password and salt. If input_file is a folder, all the files inside the folder will be encrypted:
python aes_cipher_app.py -m enc -p test_pwd -i input_file -o encrypted -s test_salt
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Decrypt the previous file:
python aes_cipher_app.py -m dec -p test_pwd -i encrypted -o decrypted -s test_salt
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Encrypt multiple files one time with the given password and salt. If one of the input files is a directory, it will be discarded:
python aes_cipher_app.py -m enc -p test_pwd -i input_file1,input_file2,input_file3 -o encrypted -s test_salt
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Encrypt a file 3 times using 3 passwords with random salts and custom number of iteration:
python aes_cipher_app.py -m enc -p test_pwd_1,test_pwd_2,test_pwd_3 -t 131072 -i input_file -o encrypted
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Decrypt the previous file:
python aes_cipher_app.py -m dec -p test_pwd_1,test_pwd_2,test_pwd_3 -t 131072 -i encrypted -o decrypted