Utilities

Generating Random Bytes

monocypher.utils.random(n)

Generates exactly n random bytes. This just calls os.urandom() and returns the result.

Return type:

bytes

Constant-Time Comparisons

The following functions perform constant-time comparisons of bytes objects of length 16, 32, and 64 respectively. They return True if they are equal, and False otherwise.

monocypher.utils.crypto_verify16(a, b)
monocypher.utils.crypto_verify32(a, b)
monocypher.utils.crypto_verify64(a, b)
from monocypher.utils import crypto_verify16
crypto_verify16(b'a....a', b'a....a')

Copying Contexts

monocypher.utils.copy_context(ctx_ptr, type)

Return a copy of the struct at ctx_ptr of the given type. This can be used to copy structs, e.g. crypto_blake2b_ctx. This is equivalent to the following in C:

type dst_ptr = malloc(sizeof(*ctx_ptr));
memcpy(
    (void *) dst_ptr,
    (void *) ctx_ptr,
    sizeof(*ctx_ptr)
);

Example:

>>> from monocypher.bindings import crypto_blake2b_init
>>> ctx = crypto_blake2b_init()
>>> u = copy_context(ctx, 'crypto_blake2b_ctx *')
<cdata 'crypto_blake2b_ctx *' owning ...>
>>> u == ctx
False
Parameters:

  • ctx_ptr – CFFI pointer to some struct.

  • type – Type of ctx_ptr.

Memory Wipe

monocypher.utils.crypto_wipe(buf)

Wipe the given buf by filling it with zeros. Example:

>>> buf = bytearray(b'abc')
>>> crypto_wipe(buf)
>>> buf
bytearray(b'\x00\x00\x00')
Parameters:

buf – Any writable object with the buffer protocol, e.g. bytearray or array.array.