low level cryptographic library (public-key cryptos)

 Nettle is a cryptographic library that is designed to fit easily in more or
 less any context: In crypto toolkits for object-oriented languages (C++,
 Python, Pike, ...), in applications like LSH or GNUPG, or even in kernel
 space.
 .
 It tries to solve a problem of providing a common set of cryptographic
 algorithms for higher-level applications by implementing a
 context-independent set of cryptographic algorithms. In that light, Nettle
 doesn't do any memory allocation or I/O, it simply provides the
 cryptographic algorithms for the application to use in any environment and
 in any way it needs.
 .
 This package contains the asymmetric cryptographic algorithms, which,
 require the GNU multiple precision arithmetic library (libgmp) for
 their large integer computations.