To build on UNIX-like systems, BIND requires support for POSIX.1c threads (IEEE Std 1003.1c-1995), the Advanced Sockets API for IPv6 (RFC 3542), and standard atomic operations provided by the C compiler. The OpenSSL cryptography library must be available for the target platform. A PKCS#11 provider can be used instead for Public Key cryptography (i.e., DNSSEC signing and validation), but OpenSSL is still required for general cryptography operations such as hashing and random number generation. More information can be found in the PLATFORMS.md file that is included in the source distribution of BIND 9. If your compiler and system libraries provide the above features, BIND 9 should compile and run. If that isn't the case, the BIND development team will generally accept patches that add support for systems that are still supported by their respective vendors.