+
+/* asymetric (public key) crypto */
+
+/** Opaque structure for public and private keys. */
+struct asymmetric_key;
+
+int pub_encrypt(struct asymmetric_key *pub, unsigned char *inbuf,
+ unsigned len, unsigned char *outbuf);
+int priv_decrypt(const char *key_file, unsigned char *outbuf,
+ unsigned char *inbuf, int inlen);
+int get_asymmetric_key(const char *key_file, int private,
+ struct asymmetric_key **result);
+void free_asymmetric_key(struct asymmetric_key *key);
+
+/* random numbers */
+void get_random_bytes_or_die(unsigned char *buf, int num);
+void init_random_seed_or_die(void);
+
+/* stream cipher declarations and prototypes */
+
+/** Opaque structure for stream ciphers. */
+struct stream_cipher;
+/** Number of bytes of the session key for stream ciphers. */
+#define SESSION_KEY_LEN 32
+/**
+ * Used for client-server communication encryption.
+ *
+ * The traffic between (the forked child of) para_server and the remote client
+ * process is crypted by a symmetric session key. This structure contains the
+ * keys for the stream cipher and the file descriptor for which these keys
+ * should be used.
+ */
+struct stream_cipher_context {
+ /** The socket file descriptor. */
+ int fd;
+ /** Key used for receiving data. */
+ struct stream_cipher *recv;
+ /** Key used for sending data. */
+ struct stream_cipher *send;
+};
+struct stream_cipher *sc_new(const unsigned char *data, int len);
+void sc_free(struct stream_cipher *sc);
+int sc_send_bin_buffer(struct stream_cipher_context *scc, char *buf,
+ size_t len);
+int sc_send_buffer(struct stream_cipher_context *scc, char *buf);
+__printf_2_3 int sc_send_va_buffer(struct stream_cipher_context *scc,
+ const char *fmt, ...);
+int sc_recv_bin_buffer(struct stream_cipher_context *scc, char *buf,
+ size_t size);
+int sc_recv_buffer(struct stream_cipher_context *scc, char *buf, size_t size);
+
+/* hashing */
+
+/** Size of the hash value in bytes. */
+#define HASH_SIZE 20
+
+void hash_function(const char *data, unsigned long len, unsigned char *hash);
+void hash_to_asc(unsigned char *hash, char *asc);
+int hash_compare(unsigned char *h1, unsigned char *h2);