13.4 Multi-Precision-Integer Subsystem Architecture
The implementation of Libgcrypt's big integer computation code is
based on an old release of GNU Multi-Precision Library (GMP). The
decision not to use the GMP library directly was due to stalled
development at that time and due to security requirements which could
not be provided by the code in GMP. As GMP does, Libgcrypt provides
high performance assembler implementations of low level code for
several CPUS to gain much better performance than with a generic C
Major features of Libgcrypt's multi-precision-integer code compared to
- Avoidance of stack based allocations to allow protection against
swapping out of sensitive data and for easy zeroing of sensitive
- Optional use of secure memory and tracking of its use so that results
are also put into secure memory.
- MPIs are identified by a handle (implemented as a pointer) to give
better control over allocations and to augment them with extra
properties like opaque data.
- Removal of unnecessary code to reduce complexity.
- Functions specialized for public key cryptography.