## secure-random

2016-02-08

Cryptographically secure pseudo-random number generator for Common Lisp

### Upstream URL

### Author

Anton Vodonosov <avodonosov@yandex.ru>

### License

MIT

README

Provided Systems

Overview.
~~~~~~~~~
secure-random provides a cryptographically secure pseudo-random
number generator (CSPRNG) for Common Lisp.
Example: (SECURE-RANDOM:NUMBER 10) => 9
We define an abstract interface for CSPRNG and provide a default
implementation of that interface.
The library API.
~~~~~~~~~~~~~~~~
Class SECURE-RANDOM:GENERATOR.
The base class for all the possible implementations
of a secure random number generator.
Special variable SECURE-RANDOM:*GENERATOR*.
Current value of the random number generator. Used as
the default value for the library functions parameter GENERATOR.
Generic function BYTES (COUNT GENERATOR) => random bytes.
The only generic function which needs to be implemented
by a subclass of SECURE-RANDOM:GENERATOR. Generates COUNT
cryptographically strong pseudo-random bytes using the random
number generator GENERATOR. Returns the bytes as a SIMPLE-ARRAY
with ELEMENT-TYPE '(UNSIGNED-BYTE 8). Signals an ERROR in case
of problems (for example when the random number generator
failed to initialize itself with enough entrophy).
Function NUMBER (LIMIT &optional (GENERATOR *GENERATOR*)) => random number.
Returns a cryptographically strong pseudo-random number that
is a non-negative number less than LIMIT and of the same
type as LIMIT (in the current implementation, only INTEGER
type is supporeted). LIMIT is a positive number. GENERATOR is an
instance of a subclass of the SECURE-RANDOM:GENERATOR. Signals
an ERROR in case of problems (for example when the random
number generator failed to initialize itself with enough entrophy).
Implementation notes.
~~~~~~~~~~~~~~~~~~~~~
The default implementation uses OpenSSL random number generator (via cl+ssl
library). We started from the OpenSSL usage because it's the simplest way.
Implementation of a pure Common Lisp CSPRNG is desirable, but it would
require to write much more code. The problem is not in the CSPRNG algorithms
themself, which are relatively simple (just read for example the Wikipedia article,
and use Ironclad for the required building blocks). But the problem is in
initialization of CSPRNG. Any CSPRNG needs to be initialized by some unguessable
value. OpenSSL can gather the initial value from a platform specific service
(/dev/random on Unix'es where it present, Windows Crypto API,
Entropy Gathering Daemon, etc.). The pure Lisp CSPRNG library would need to
re-implement all this code for gathering a truly unguessable initial value.
Contact.
~~~~~~~~
Send questions or comments to avodonosov@yandex.ru