- secretsharing api proposal

1 files changed, 204 insertions, 0 deletions

diff --git a/src/include/gnunet_secretsharing_service.h b/src/include/gnunet_secretsharing_service.h
new file mode 100644
index 000000000..f8235fb36
--- /dev/null
+++ b/src/include/gnunet_secretsharing_service.h
@@ -0,0 +1,204 @@
+/*
+      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 verified additive secret sharing and cooperative decryption
+ * @author Florian Dold
+ */
+
+#ifndef GNUNET_CONSENSUS_SERVICE_H
+#define GNUNET_CONSENSUS_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 <gcrypt.h>
+
+
+/**
+ * Session that will eventually establish a shared secred between
+ * the involved peers and allow encryption and cooperative decryption.
+ */
+struct GNUNET_SECRETSHARING_Session;
+
+
+/**
+ * Handle to cancel a cooperative decryption operation.
+ */
+struct GNUNET_SECRETSHARING_DecryptionHandle;
+
+
+/**
+ * Parameters of the crypto system.
+ */
+struct GNUNET_SECRETSHARING_Parameters
+{
+  /**
+   * 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;
+};
+
+
+/**
+ * Encrypted field element.
+ */
+struct GNUNET_SECRETSHARING_Ciphertext 
+{
+  /**
+   * First component.
+   */
+  gcry_mpi_t c1;
+  /**
+   * Second component.
+   */
+  gcry_mpi_t c2;
+};
+
+
+/**
+ * Called once the secret has been established.
+ *
+ * @param cls closure
+ * @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
+ *                    the shared secret
+ */
+typedef void (*GNUNET_SECRETSHARING_SecretReadyCallback) (void *cls,
+                                                          gcry_mpi_t public_key,
+                                                          unsigned int num_ready_peers,
+                                                          const struct GNUNET_PeerIdentity *ready_peers);
+
+
+/**
+ * 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 session_id unique session id
+ * @param deadline point in time where the session must be established; taken as hint
+ *                 by underlying consensus sessions
+ * @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,
+                                     struct GNUNET_SECRETSHARING_Parameters *parameters,
+                                     GNUNET_SECRETSHARING_SecretReadyCallback *cb,
+                                     void *cls);
+
+
+/**
+ * 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 session session to take the key for encryption from,
+ *                the session's ready callback must have been already called
+ * @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)
+ */
+int 
+GNUNET_SECRETSHARING_encrypt (const struct GNUNET_SECRETSHARING_Session *session,
+                              gcry_mpi_t message,
+                              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 session session to use for the 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
+ * @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);
+
+/**
+ * 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.
+ */
+void
+GNUNET_SECRETSHARING_cancel_decrypt (struct GNUNET_SECRETSHARING_DecryptionHandle *decryption_handle);
+
+
+
+
+
+#if 0                           /* keep Emacsens' auto-indent happy */
+{
+#endif
+#ifdef __cplusplus
+}
+#endif
+
+#endif