libgcrypt

Libgcrypt is a general-purpose cryptographic library developed as part of the GNU project. It provides a comprehensive set of cryptographic primitives and services through a C API, designed to be portable across platforms. It is widely used by GnuPG (GPG) and by many other free and open-source projects to perform encryption, decryption, digital signatures, and related operations.

The library offers support for symmetric and asymmetric cryptography, including a variety of ciphers, hash functions, and public-key algorithms. It includes mechanisms for message authentication, key derivation, and password-based encryption, as well as a secure random number generator. Libgcrypt emphasizes a modular architecture with support for multiple backends and, where available, hardware acceleration to improve performance and security.

Libgcrypt provides both low-level and higher-level APIs, enabling developers to integrate cryptographic functionality directly or to use higher-level constructs to simplify common tasks. The design focuses on portability, cross-platform compatibility, and a clean C interface, along with attention to security considerations such as constant-time implementations for critical operations where feasible.

The library is licensed under the GNU Lesser General Public License (LGPL), allowing it to be linked with proprietary software while remaining free software. It is maintained by the Free Software Foundation as part of the GNU project and has a broad ecosystem of adopters beyond GnuPG. Libgcrypt’s ongoing development aims to improve security, provide up-to-date algorithms, and maintain compatibility with evolving cryptographic standards.