SHA256_DIGEST_STRING_LENGTH
char *SHA256_End(SHA256_CTX* context, char buffer[SHA256_DIGEST_STRING_LENGTH]) {
char* SHA256_Data(const sha2_byte* data, size_t len, char digest[SHA256_DIGEST_STRING_LENGTH]) {
char* SHA256_End(SHA256_CTX*, char[SHA256_DIGEST_STRING_LENGTH]);
char* SHA256_Data(const u_int8_t*, size_t, char[SHA256_DIGEST_STRING_LENGTH]);