/* This file is part of GNUnet (C) 2013 Christian Grothoff (and other contributing authors) GNUnet is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version. GNUnet is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GNUnet; see the file COPYING. If not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ /** * @file include/gnunet_secretsharing_service.h * @brief verifiable additive secret sharing and cooperative decryption * @author Florian Dold */ #ifndef GNUNET_SECRETSHARING_SERVICE_H #define GNUNET_SECRETSHARING_SERVICE_H #ifdef __cplusplus extern "C" { #if 0 /* keep Emacsens' auto-indent happy */ } #endif #endif #include "platform.h" #include "gnunet_common.h" #include "gnunet_time_lib.h" #include "gnunet_configuration_lib.h" #include /** * 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. */ struct GNUNET_SECRETSHARING_DecryptionHandle; /** * Public key of a group sharing a secret. */ struct GNUNET_SECRETSHARING_PublicKey { uint32_t bits[GNUNET_SECRETSHARING_KEY_BITS / 8 / sizeof (uint32_t)]; }; /** * Encrypted field element. */ 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 { /** * Value of the message. */ 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 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 @a ready_peers * @param ready_peers peers that successfuly participated in establishing * the shared secret */ typedef void (*GNUNET_SECRETSHARING_SecretReadyCallback) (void *cls, 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 data decrypted value * @param data_size number of bytes in @a data */ typedef void (*GNUNET_SECRETSHARING_DecryptCallback) (void *cls, const void *data, size_t data_size); /** * Create a session that will eventually establish a shared secret * with the other peers. * * @param cfg configuration to use * @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 */ struct GNUNET_SECRETSHARING_Session * GNUNET_SECRETSHARING_create_session (const struct GNUNET_CONFIGURATION_Handle *cfg, unsigned int num_peers, const struct GNUNET_PeerIdentity *peers, const struct GNUNET_HashCode *session_id, struct GNUNET_TIME_Absolute deadline, 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. * * @param session session to destroy */ void GNUNET_SECRETSHARING_destroy_session (struct GNUNET_SECRETSHARING_Session *session); /** * Encrypt a value. This operation is executed locally, no communication is * necessary. * * This is a helper function, encryption can be done soley with a session's public key * and the crypto system parameters. * * @param public_key public key to use for decryption * @param message message to encrypt * @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 (struct GNUNET_SECRETSHARING_PublicKey *public_key, const void *message, size_t message_size, struct GNUNET_SECRETSHARING_Ciphertext *result_ciphertext); /** * Publish the given ciphertext for decryption. Once a sufficient (>=k) number of peers has * published the same value, it will be decrypted. * * 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 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 decrypt_cb_cls closure for @a decrypt_cb * @return handle to cancel the operation */ struct GNUNET_SECRETSHARING_DecryptionHandle * GNUNET_SECRETSHARING_decrypt (struct GNUNET_SECRETSHARING_Share *share, struct GNUNET_SECRETSHARING_Ciphertext *ciphertext, GNUNET_SECRETSHARING_DecryptCallback decrypt_cb, void *decrypt_cb_cls); /** * Cancel a decryption. * * 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 decryption_handle decryption to cancel */ void 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 */ { #endif #ifdef __cplusplus } #endif #endif