API of the ‘gostcrypto.gostrandom’ module

Introduction

The module that implements pseudo-random sequence generation in accordance with R 1323565.1.006-2017. The module includes the R132356510062017 and GOSTRandomError classes, the new function and constants.

Constants

  • SIZE_S_384 - the size of the initial filling (seed) is 384 bits.
  • SIZE_S_320 - the size of the initial filling (seed) is 320 bits.
  • SIZE_S_256 - the size of the initial filling (seed) is 256 bits.

Note

The specified values for the initial fill size are recommended in R 1323565.1.006-2017. It is possible to use other values that meet the requirements presented out in R 1323565.1.006-2017.

Functions

new(rand_size, **kwargs)

Creates a new pseudo-random sequence generation object and returns it.
import gostcrypto

random_k = bytearray([
    0xa8, 0xe2, 0xf9, 0x00, 0xdd, 0x4d, 0x7e, 0x24,
    0x5f, 0x09, 0x75, 0x3d, 0x01, 0xe8, 0x75, 0xfc,
    0x38, 0xf1, 0x4f, 0xf5, 0x25, 0x4c, 0x94, 0xea,
    0xdb, 0x45, 0x1e, 0x4a, 0xb6, 0x03, 0xb1, 0x47,
])
random_obj = gostcrypto.gostrandom.new(64,
                                       random_k=random_k,
                                       size_s=gostcrypto.gostrandom.SIZE_S_256)

Arguments:

  • rand_size - size of the generated random variable (in bytes).

Keyword arguments:

  • rand_k - initial filling (seed). If this argument is not passed to the function, the os.urandom function is used to generate the initial filling.
  • size_s - size of the initial filling (in bytes). The default value is SIZE_S_384.

Return:

  • New pseudo-random sequence generation object (as an instance of the R132356510062017 class).

Exceptions:

  • GOSTRandomError(‘invalid seed value size’) - in case of invalid size of initial filling.

Classes

R132356510062017

Class that implements pseudo-random sequence generation in accordance with R 1323565.1.006-2017.

Methods:

random()
Generating the next value from a pseudo-random sequence.
import gostcrypto

random_obj = gostcrypto.gostrandom.new(32)
random_result = random_obj.random()

Return:

  • New random value (as a byte object).

Exception:

  • GOSTRandomError(‘exceeded the limit value of the counter’) - when the counter limit is exceeded.
  • GOSTRandomError(‘the seed value is zero’) - if the seed value is zero.
reset(rand_k)
Resetting the counter and setting a new initial filling.
import gostcrypto

rand_k_1 = bytearray([
    0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
    0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
    0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
    0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
])

rand_k_2 = bytearray([
    0xa8, 0xe2, 0xf9, 0x00, 0xdd, 0x4d, 0x7e, 0x24,
    0x5f, 0x09, 0x75, 0x3d, 0x01, 0xe8, 0x75, 0xfc,
    0x38, 0xf1, 0x4f, 0xf5, 0x25, 0x4c, 0x94, 0xea,
    0xdb, 0x45, 0x1e, 0x4a, 0xb6, 0x03, 0xb1, 0x47,
])

random_obj = gostcrypto.gostrandom.new(32,
                                       rand_k=rand_k_1,
                                       size_s=gostcrypto.gostrandom.SIZE_S_256)
random_result_1 = random_obj.random()
random_obj.reset(rand_k_2)
random_result_2 = random_obj.random()

Arguments:

  • rand_k - new initial filling (seed). If this argument is not passed to the function, the os.urandom function is used to generate the initial filling.

Exception:

  • GOSTRandomError(‘invalid seed value size’) - in case of invalid size of initial filling.
clear()
Clearing the counter value.
import gostcrypto

random_obj = gostcrypto.gostrandom.new(32)
random_obj.clear()

GOSTRandomError

The class that implements exceptions.
import gostcrypto

random_k = bytearray([
    0xa8, 0xe2, 0xf9, 0x00, 0xdd, 0x4d, 0x7e, 0x24,
    0x5f, 0x09, 0x75, 0x3d, 0x01, 0xe8, 0x75, 0xfc,
    0x38, 0xf1, 0x4f, 0xf5, 0x25, 0x4c, 0x94, 0xea,
    0xdb, 0x45, 0x1e, 0x4a, 0xb6, 0x03, 0xb1, 0x47,
])
try:
    random_obj = gostcrypto.gostrandom.new(64,
                                           random_k=random_k,
                                           size_s=gostcrypto.gostrandom.SIZE_S_256)
    random_result = random_obj.random()
except gostcrypto.gostrandom.GOSTRandomError as err:
    print(err)
else:
    print(random_result.hex())

Exception types:

  • invalid seed value - in case of invalid value of initial filling.
  • exceeded the limit value of the counter - when the counter limit is exceeded.
  • the seed value is zero - if the seed value is zero.

Example of use

import gostcrypto

rand_k = bytearray([
    0x88, 0x99, 0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff,
    0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77,
    0xfe, 0xdc, 0xba, 0x98, 0x76, 0x54, 0x32, 0x10,
    0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef,
])

random_obj = gostcrypto.gostrandom.new(32,
                                       rand_k=rand_k,
                                       size_s=gostcrypto.gostrandom.SIZE_S_256)
random_result = random_obj.random()
random_obj.clear()