/**
* @file include/gnunet_secretsharing_service.h
- * @brief verified additive secret sharing and cooperative decryption
+ * @brief verifiable additive secret sharing and cooperative decryption
* @author Florian Dold
*/
#include <gcrypt.h>
+/**
+ * Number of bits for secretsharing keys.
+ * Must be smaller than the Pallier key size used internally
+ * by the secretsharing service.
+ */
+#define GNUNET_SECRETSHARING_KEY_BITS 1024
+
+
/**
* Session that will eventually establish a shared secred between
* the involved peers and allow encryption and cooperative decryption.
*/
struct GNUNET_SECRETSHARING_Session;
+/**
+ * Share of a secret shared with a group of peers.
+ * Contains both the share and information about the peers that have
+ * the other parts of the share.
+ */
+struct GNUNET_SECRETSHARING_Share;
+
/**
* Handle to cancel a cooperative decryption operation.
/**
- * Parameters of the crypto system.
+ * Public key of a group sharing a secret.
*/
-struct GNUNET_SECRETSHARING_Parameters
+struct GNUNET_SECRETSHARING_PublicKey
{
- /**
- * Threshold, that is, minimum number of peers that
- * must cooperate to decrypt a value.
- */
- unsigned int k;
- /**
- * Prime with p = 2q+1.
- */
- gcry_mpi_t p;
- /**
- * Prime.
- */
- gcry_mpi_t q;
- /**
- * Generator of G_q.
- */
- gcry_mpi_t g;
+ uint32_t bits[GNUNET_SECRETSHARING_KEY_BITS / 8 / sizeof (uint32_t)];
};
/**
* Encrypted field element.
*/
-struct GNUNET_SECRETSHARING_Ciphertext
+struct GNUNET_SECRETSHARING_Ciphertext
+{
+ uint32_t bits[2 * GNUNET_SECRETSHARING_KEY_BITS / 8 / sizeof (uint32_t)];
+};
+
+
+/**
+ * Plain, unencrypted message that can be encrypted with
+ * a group public key.
+ */
+struct GNUNET_SECRETSHARING_Message
{
/**
- * First component.
- */
- gcry_mpi_t c1;
- /**
- * Second component.
+ * Value of the message.
*/
- gcry_mpi_t c2;
+ gcry_mpi_t value;
};
/**
* Called once the secret has been established with all peers, or the deadline is due.
*
- * Note that the number of peers can be smaller that 'k' (this threshold parameter), which
- * makes the threshold crypto system useledd. However, in this case one can still determine which peers
+ * Note that the number of peers can be smaller than 'k' (this threshold parameter), which
+ * makes the threshold crypto system useless. However, in this case one can still determine which peers
* were able to participate in the secret sharing successfully.
*
+ * If the secret sharing failed, num_ready_peers is 0 and my_share and public_key is NULL.
+ *
* @param cls closure
+ * @param my_share the share of this peer
* @param public_key public key of the session
- * @param num_ready_peers number of peers in @ready_peers
- * @parem ready_peers peers that successfuly participated in establishing
+ * @param num_ready_peers number of peers in @a ready_peers
+ * @param ready_peers peers that successfuly participated in establishing
* the shared secret
*/
typedef void (*GNUNET_SECRETSHARING_SecretReadyCallback) (void *cls,
- gcry_mpi_t public_key,
+ const struct GNUNET_SECRETSHARING_Share *my_share,
+ const struct GNUNET_SECRETSHARING_PublicKey *public_key,
unsigned int num_ready_peers,
const struct GNUNET_PeerIdentity *ready_peers);
* Called when a decryption has succeeded.
*
* @param cls closure
- * @param result decrypted value
+ * @param data decrypted value
+ * @param data_size number of bytes in @a data
*/
typedef void (*GNUNET_SECRETSHARING_DecryptCallback) (void *cls,
- gcry_mpi_t result);
+ const void *data,
+ size_t data_size);
/**
* with the other peers.
*
* @param cfg configuration to use
- * @param num_peers number of peers in @peers
+ * @param num_peers number of peers in 'peers'
+ * @param peers array of peers that we will share secrets with, can optionally contain the local peer
* @param session_id unique session id
* @param deadline point in time where the session must be established; taken as hint
* by underlying consensus sessions
+ * @param threshold minimum number of peers that must cooperate to decrypt a value
* @param cb called when the secret has been established
* @param cls closure for cb
*/
const struct GNUNET_PeerIdentity *peers,
const struct GNUNET_HashCode *session_id,
struct GNUNET_TIME_Absolute deadline,
- struct GNUNET_SECRETSHARING_Parameters *parameters,
- GNUNET_SECRETSHARING_SecretReadyCallback *cb,
+ unsigned int threshold,
+ GNUNET_SECRETSHARING_SecretReadyCallback cb,
void *cls);
+/**
+ * Destroy a secret share.
+ *
+ * @param share secret share to destroy
+ */
+void
+GNUNET_SECRETSHARING_share_destroy (const struct GNUNET_SECRETSHARING_Share *share);
+
+
/**
* Destroy a secret sharing session.
*
* This is a helper function, encryption can be done soley with a session's public key
* and the crypto system parameters.
*
- * @param session session to take the key for encryption from,
- * the session's ready callback must have been already called
+ * @param public_key public key to use for decryption
* @param message message to encrypt
- * @param result_cyphertext pointer to store the resulting ciphertext
- * @return GNUNET_YES on succes, GNUNET_SYSERR if the message is invalid (invalid range)
+ * @param message_size number of bytes in @a message
+ * @param result_ciphertext pointer to store the resulting ciphertext
+ * @return #GNUNET_YES on succes, #GNUNET_SYSERR if the message is invalid (invalid range)
*/
-int
-GNUNET_SECRETSHARING_encrypt (const struct GNUNET_SECRETSHARING_Session *session,
- gcry_mpi_t message,
+int
+GNUNET_SECRETSHARING_encrypt (struct GNUNET_SECRETSHARING_PublicKey *public_key,
+ const void *message,
+ size_t message_size,
struct GNUNET_SECRETSHARING_Ciphertext *result_ciphertext);
* When the operation is canceled, the decrypt_cb is not called anymore, but the calling
* peer may already have irrevocably contributed his share for the decryption of the value.
*
- * @param session session to use for the decryption
+ * @param share our secret share to use for decryption
* @param ciphertext ciphertext to publish in order to decrypt it (if enough peers agree)
* @param decrypt_cb callback called once the decryption succeeded
- * @param cls closure for decrypt_cb
+ * @param decrypt_cb_cls closure for @a decrypt_cb
* @return handle to cancel the operation
*/
struct GNUNET_SECRETSHARING_DecryptionHandle *
-GNUNET_SECRETSHARING_publish_decrypt (struct GNUNET_SECRETSHARING_Session *session,
- struct GNUNET_SECRETSHARING_Ciphertext *ciphertext,
- GNUNET_SECRETSHARING_DecryptCallback decrypt_cb,
- void *cls);
+GNUNET_SECRETSHARING_decrypt (struct GNUNET_SECRETSHARING_Share *share,
+ struct GNUNET_SECRETSHARING_Ciphertext *ciphertext,
+ GNUNET_SECRETSHARING_DecryptCallback decrypt_cb,
+ void *decrypt_cb_cls);
/**
* @param decryption_handle decryption to cancel
*/
void
-GNUNET_SECRETSHARING_cancel_decrypt (struct GNUNET_SECRETSHARING_DecryptionHandle *decryption_handle);
+GNUNET_SECRETSHARING_decrypt_cancel (struct GNUNET_SECRETSHARING_DecryptionHandle *decryption_handle);
+
+
+/**
+ * Read a share from its binary representation.
+ *
+ * @param data binary representation of the share
+ * @param len length of @a data
+ * @return the share, or NULL on error
+ */
+struct GNUNET_SECRETSHARING_Share *
+GNUNET_SECRETSHARING_share_read (void *data, size_t len);
+
+
+/**
+ * Convert a share to its binary representation. Use
+ * #GNUNET_SECRETSHARING_share_size to get the necessary size for the binary
+ * representation.
+ *
+ * @param share share to write
+ * @param buf buffer to write to
+ * @param buflen number of writable bytes in @a buffer
+ * @param[out] writelen pointer to store number of bytes written,
+ * ignored if NULL
+ * @return GNUNET_YES on success, GNUNET_NO on failure
+ */
+int
+GNUNET_SECRETSHARING_share_write (struct GNUNET_SECRETSHARING_Share *share,
+ void *buf, size_t buflen, size_t *writelen);
+
+
+/**
+ * Get the number of bytes necessary to represent the given share.
+ *
+ * @param share share
+ * @return number of bytes necessary to represent @a share
+ */
+size_t
+GNUNET_SECRETSHARING_share_size (struct GNUNET_SECRETSHARING_Share *share);
+
#if 0 /* keep Emacsens' auto-indent happy */
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