hsl20_4_crypto.hsl20_4_crypto.AESCipher Class Reference

Class for data encryption using AES. More..

Public Member Functions
def	__init__ (self)
	Constructor. More...
def	init (self, key, iv=None)
	Initialize. More...
def	use_ecb (self)
	Uses the ECB (Electronic Code Book) mode for encryption More...
def	use_cbc (self)
	Uses the CBC (Cipher Block Chaining) mode for encryption
def	use_cfb (self)
	Uses the CFB (Cipher FeedBack) mode for encryption
def	use_ofb (self)
	Uses the OFB (Output FeedBack) mode for encryption
def	use_ctr (self)
	Uses the CTR (Counter Mode) for encryption
def	encrypt (self, data)
	Encrypts the transmitted data block. More...
def	decrypt (self, data)
	Decrypts the transferred data block. More...

Static Public Member Functions
def	generate_init_vector ()
	Generates a 16 characters long string. More...

Detailed Description

Class for encrypting data using AES

Part of the packet for encryption.

The methods encrypt (encrypt) and decrypt (decrypt) are used to process whole strings. By default CBC (Cipher-Block Chaining) is used

class Crypto_AES(hsl20_4.BaseModule):

    def __init__(self, homeserver_context):
        ....
        

    def on_input_value(self, index, value):
        if index == self.PIN_I_DO_CRYPTO:
            data = "val_with_16_char
            vector = "abcdefghijklmnop"

            aes_1 = self.FRAMEWORK.create_aes()
            aes_1.init("key_with_16_char" , vector)
            aes_1.use_cbc()
            encrypted = aes_1.encrypt(data)

            aes_2 = self.FRAMEWORK.create_aes()
            aes_2.init("key_with_16_char" , vector)
            aes_2.use_cbc()
            decrypted = aes_2.decrypt(encrypted)

If a telegram is received at input PIN_I_DO_CRYPTO, the data block data is encrypted with the static vector vector (aes_1) and stored in the variable encrypted.
The encrypted data block encrypted is then decrypted again with the same vector (aes_2) and stored in the variable decrypted.
In both cases the method CBC is used.

Note

The data blocks decrypted and data are identical!
The same AES object cannot be used for encryption and decryption!

Constructor & Destructor Documentation

__init__()

def hsl20_4_crypto.hsl20_4_crypto.AESCipher.__init__

(

self

)

Constructor

Warning

This class should not be instantiated directly

Member Function Documentation

decrypt()

def hsl20_4_crypto.hsl20_4_crypto.AESCipher.decrypt	(		self,
			data
	)

Decrypts the transferred data block

Note

The complete data packet to be encrypted must always be transferred: decrypt(a)+decrypt(b) != decrypt(a+b)

Depending on the mode, the transferred data packet must be a multiple of the block size

Parameters

data	string Data block

Exceptions

AttributeError	It's triggered when... ...no key was specified ...the key has an invalid length ...an init vector has been specified which is not 16 characters long
ValueError	It's triggered when... ...the size of the data packet is not correct

encrypt()

def hsl20_4_crypto.hsl20_4_crypto.AESCipher.encrypt	(		self,
			data
	)

Encrypts the transferred data block

The entire packet to be encrypted must be transferred

Note

The complete data packet to be encrypted must always be transferred: encrypt(a)+encrypt(b) != encrypt(a+b)

Depending on the mode, the transferred data packet must be a multiple of the block size

Parameters

data	string Data block

Exceptions

AttributesError	It's triggered when... ...no key was specified ...the key has an invalid length ...an init vector has been specified which is not 16 characters long
ValueError	It's triggered when... ...the size of the data packet is not correct

generate_init_vector()

def hsl20_4_crypto.hsl20_4_crypto.AESCipher.generate_init_vector ( )

static

Generates a 16 character long string

This can be used as an init vector

Returns

string
Init vector

init()

def hsl20_4_crypto.hsl20_4_crypto.AESCipher.init	(		self,
			key,
			iv = None
	)

Initialize

Parameters

key	string Key. Must be 16, 24 or 32 in length
iv	string Optional. Init vector, must be 16 characters long

use_ecb()

def hsl20_4_crypto.hsl20_4_crypto.AESCipher.use_ecb

(

self

)

Uses the ECB (Electronic Code Book) mode for encryption

Note

This method does not require an init vector!

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The documentation for this class was generated from the following file:

• hsl20_4_crypto.py