Consolidated all the crypto apis and implemented the Precomputation Postprocessing step

15 files changed, 235 insertions, 127 deletions

diff --git a/libcmix-common/cmixprotofunctor.hpp b/libcmix-common/cmixprotofunctor.hpp
index 5fd736b..755894e 100644
--- a/libcmix-common/cmixprotofunctor.hpp
+++ b/libcmix-common/cmixprotofunctor.hpp
@@ -30,49 +30,54 @@ struct CMixProtoFunctor {
 	} \
 
 	/*!
-	* #MESSAGE_SETTER_DECL(Initialization, initialization)
+	* #MESSAGE_SETTER_DEF(Initialization, initialization)
 	*/
 	MESSAGE_SETTER_DEF(Initialization, initialization)
 	
 	/*!
-	* #MESSAGE_SETTER_DECL(ImANode, imanode)
+	* #MESSAGE_SETTER_DEF(ImANode, imanode)
 	*/
 	MESSAGE_SETTER_DEF(ImANode, imanode)
 	
 	/*!
-	* #MESSAGE_SETTER_DECL(ImAClient, imaclient)
+	* #MESSAGE_SETTER_DEF(ImAClient, imaclient)
 	*/
 	MESSAGE_SETTER_DEF(ImAClient, imaclient)
 	
 	/*!
-	* #MESSAGE_SETTER_DECL(Bye, bye)
+	* #MESSAGE_SETTER_DEF(Bye, bye)
 	*/
 	MESSAGE_SETTER_DEF(Bye, bye)
 	
 	/*!
-	* #MESSAGE_SETTER_DECL(KeyExchange, keyexchange)
+	* #MESSAGE_SETTER_DEF(KeyExchange, keyexchange)
 	*/
 	MESSAGE_SETTER_DEF(KeyExchange, keyexchange)
 	
 	/*!
-	* #MESSAGE_SETTER_DECL(SecretKey, secretkey)
+	* #MESSAGE_SETTER_DEF(SecretKey, secretkey)
 	*/
 	MESSAGE_SETTER_DEF(SecretKey, secretkey)
 	
 	/*!
-	 * #MESSAGE_SETTER_DECL(NodeReady, nodeready)
+	 * #MESSAGE_SETTER_DEF(NodeReady, nodeready)
 	 */
 	MESSAGE_SETTER_DEF(NodeReady, nodeready)
 	
 	/*!
-	 * #MESSAGE_SETTER_DECL(PrePre, prepre)
+	 * #MESSAGE_SETTER_DEF(PrePre, prepre)
 	 */
 	MESSAGE_SETTER_DEF(PrePre, prepre)
 	
 	/*!
-	 * #MESSAGE_SETTER_DECL(PreMix, premix)
+	 * #MESSAGE_SETTER_DEF(PreMix, premix)
 	 */
 	MESSAGE_SETTER_DEF(PreMix, premix)
+	
+	/*!
+	 * #MESSAGE_SETTER_DEF(PrePost, prepost)
+	 */
+	MESSAGE_SETTER_DEF(PrePost, prepost)
 
 	#undef MESSAGE_SETTER_DEF
 };
diff --git a/libcmix-crypto/api.h b/libcmix-crypto/api.h
index 6d701d7..addf9e3 100644
--- a/libcmix-crypto/api.h
+++ b/libcmix-crypto/api.h
@@ -96,6 +96,11 @@ typedef void(*GroupElementDeleter)(GroupElement);
 typedef void (*Encrypter)(GroupElement*, GroupElement*, GroupElement, GroupElement);
 
 /*!
+ *
+ */
+typedef GroupElement (*DecryptionShareGetter)(GroupElement, GroupElement);
+
+/*!
  * \brief The Api struct stores pointers to functions of a specific implementation. Like a Curve25519 specific one.
  */
 struct Api {
@@ -110,6 +115,7 @@ struct Api {
 	GroupElementDeleter free_group_element; ///< frees a base type of the cryptolibrary.
 	KeyExchangeValueGetter get_key_exchange_value; ///< get generator *op* group element.
 	GroupElementMultiplier multiply; ///< Multiplies two groupelements modulo group.
+	DecryptionShareGetter get_decryption_share; ///< calculates the first argument to the power of Inverse second argument;
 	PublicShareAdder add_public_share; ///< Adds the public key stored in void* to the existing share.
 	SharedKeyDeriver derive_shared_key; ///< Pointer to shared key derivation function
 	SharedKeyDeleter free_shared_key; ///< Pointer to shared key deleter function
diff --git a/libcmix-crypto/curve25519/curve25519.c b/libcmix-crypto/curve25519/curve25519.c
index db77d9a..a963840 100644
--- a/libcmix-crypto/curve25519/curve25519.c
+++ b/libcmix-crypto/curve25519/curve25519.c
@@ -5,22 +5,23 @@ struct Api get_curve25519_implementation()
 {
 	curve25519_initialize();
 	return (struct Api) {
-		&curve25519_initialize,
-		&curve25519_create_keypair,
-		&curve25519_keypair_deleter,
-		&curve25519_key_to_array,
-		NULL,
-		NULL,
-		NULL,
-		NULL,
-		NULL,
-		NULL,
-		NULL,
-		&curve25519_add_public_share,
-		&curve25519_derive_shared_key,
-		&curve25519_shared_key_deleter,
-		NULL,
-		&curve25519_deinitialize
+		.initialize                   = curve25519_initialize,
+		.create_keypair               = curve25519_create_keypair,
+		.free_keypair                 = curve25519_delete_keypair,
+		.element_to_array             = curve25519_element_to_array,
+		.free_buffer                  = curve25519_free_buffer,
+		.array_to_element             = curve25519_array_to_element,
+		.get_group_element            = curve25519_get_group_element,
+		.get_group_element_array_size = curve25519_get_group_element_array_size,
+		.free_group_element           = curve25519_delete_group_element,
+		.get_key_exchange_value       = curve25519_get_key_exchange_value,
+		.multiply                     = curve25519_multiply,
+		.get_decryption_share         = curve25519_get_decryption_share,
+		.add_public_share             = curve25519_add_public_share,
+		.derive_shared_key            = curve25519_derive_shared_key,
+		.free_shared_key              = curve25519_delete_shared_key,
+		.encrypt                      = curve25519_encrypt,
+		.deinitialize                 = curve25519_deinitialize
 	};
 }
 
diff --git a/libcmix-crypto/curve25519/curve25519.h b/libcmix-crypto/curve25519/curve25519.h
index 762e8db..5f30915 100644
--- a/libcmix-crypto/curve25519/curve25519.h
+++ b/libcmix-crypto/curve25519/curve25519.h
@@ -10,55 +10,39 @@ extern "C" {
  * \file
  */
 
-/*!
- * \brief curve25519_initialize initilalize curve25519 library
- */
-extern void curve25519_initialize(void);
+extern Initializer curve25519_initialize;
 
-/*!
- * \brief curve25519_create_keypair
- * \return A curve25519 keypair.
- */
-extern struct KeyPair curve25519_create_keypair(void);
+extern KeyPairCreator curve25519_create_keypair;
 
-/*!
- * \brief curve25519_keypair_deleter
- * \param p The keypair to free.
- */
-extern void curve25519_keypair_deleter(struct KeyPair* p);
+extern KeyPairDeleter curve25519_delete_keypair;
 
-/*!
- * \brief curve25519_get_pubkey_array
- * \param pubkey
- * \param buffer
- * \param len
- */
-extern void curve25519_key_to_array(unsigned char** buffer, size_t* len, void* pubkey);
+extern ElementToArray curve25519_element_to_array;
 
-/*!
- * \brief curve25519_add_public_share
- * \param buffer
- * \param out_len
- * \param share
- * \param pubkey
- */
-extern void curve25519_add_public_share(char** buffer, size_t* out_len, char const* share, size_t in_len, void* pubkey);
+extern BufferDeleter curve25519_free_buffer;
 
-/*!
- * \brief curve25519_derive_shared_key
- * \param pair Our keypair.
- * \param pub_key The public key of the other party.
- * \param swap_pub_order Should we swap the order in which we feed the public keys to the hash function.
- * \return A Shared key
- */
-extern GroupElement curve25519_derive_shared_key(struct KeyPair pair, unsigned char const* other_pub, size_t pub_len, unsigned char const* value, size_t value_len, void* priv_value, bool swap_pub_order);
-/*!
- * \brief curve25519_shared_key_deleter
- * \param s the Shared key to free.
- */
-extern void curve25519_shared_key_deleter(struct SharedKey* s);
+extern ArrayToElement curve25519_array_to_element;
+
+extern GroupElementGetter curve25519_get_group_element;
+
+extern GroupElementDeleter curve25519_delete_group_element;
+
+extern KeyExchangeValueGetter curve25519_get_key_exchange_value;
+
+extern GroupElementMultiplier curve25519_multiply;
+
+extern DecryptionShareGetter curve25519_get_decryption_share;
+
+extern GroupElementArraySizeGetter curve25519_get_group_element_array_size;
+
+extern PublicShareAdder curve25519_add_public_share;
+
+extern SharedKeyDeriver curve25519_derive_shared_key;
+
+extern SharedKeyDeleter curve25519_delete_shared_key;
+
+extern Encrypter curve25519_encrypt;
 
-extern void curve25519_deinitialize(void);
+extern Deinitializer curve25519_deinitialize;
 
 /*!
  * \brief get_curve25519_implementation
diff --git a/libcmix-crypto/curve25519/null/null_curve25519.c b/libcmix-crypto/curve25519/null/null_curve25519.c
index 33fb963..d261791 100644
--- a/libcmix-crypto/curve25519/null/null_curve25519.c
+++ b/libcmix-crypto/curve25519/null/null_curve25519.c
@@ -1,31 +1,47 @@
 
-#include "api.h"
+#include "curve25519.h"
 
 #include <stddef.h>
 #include <stdbool.h>
 
-void curve25519_initialize(void){}
+void null_curve25519_initialize(void){}
 
-struct KeyPair curve25519_create_keypair(void) {
+struct KeyPair null_curve25519_create_keypair(void) {
 	return (struct KeyPair){
 		NULL,
 		NULL,
 	};
 }
 
-void curve25519_keypair_deleter(struct KeyPair* p) {}
+void null_curve25519_delete_keypair(struct KeyPair* p) {}
 
-void curve25519_get_key_array(char** buffer, size_t* len, void* key) {}
+void null_curve25519_get_key_array(char** buffer, size_t* len, void* key) {}
 
-void curve25519_add_public_share(char** buffer, size_t* len_out, char const* share, size_t in_len, void* pubkey) {}
+void null_curve25519_add_public_share(char** buffer, size_t* len_out, char const* share, size_t in_len, void* pubkey) {}
 
-void curve25519_shared_key_deleter(struct SharedKey* s) {}
+void null_curve25519_shared_key_deleter(struct SharedKey* s) {}
 
 
-struct SharedKey curve25519_derive_shared_key(struct KeyPair pair, unsigned char const* pub_key, bool swap_pub_order) {
-	return (struct SharedKey){
-		NULL,
-	};
+GroupElement null_curve25519_derive_shared_key(struct KeyPair keypair, unsigned char const* other_pub, size_t pub_len, unsigned char const* value, size_t value_len, void* priv_value, bool swap) {
+	return NULL;
 }
 
-void curve25519_deinitialize(void){}
\ No newline at end of file
+void null_curve25519_deinitialize(void){}
+
+Initializer curve25519_initialize = &null_curve25519_initialize;
+KeyPairCreator curve25519_create_keypair = &null_curve25519_create_keypair;
+KeyPairDeleter curve25519_delete_keypair = &null_curve25519_delete_keypair;
+ElementToArray curve25519_element_to_array = NULL;//&null_curve25519_element_to_array;
+BufferDeleter curve25519_free_buffer = NULL;//&null_curve25519_free_buffer;
+ArrayToElement curve25519_array_to_element = NULL;//&null_curve25519_array_to_element;
+GroupElementGetter curve25519_get_group_element = NULL;//&null_curve25519_get_group_element;
+GroupElementDeleter curve25519_delete_group_element = NULL;//&null_curve25519_delete_group_element;
+KeyExchangeValueGetter curve25519_get_key_exchange_value = NULL;//&null_curve25519_get_key_exchange_value;
+GroupElementMultiplier curve25519_multiply = NULL;//&null_curve25519_multiply;
+DecryptionShareGetter curve25519_get_decryption_share = NULL;//&null_curve25519_get_decryption_share;
+GroupElementArraySizeGetter curve25519_get_group_element_array_size = NULL;//&null_curve25519_get_group_element_array_size;
+PublicShareAdder curve25519_add_public_share = NULL;//&null_curve25519_add_public_share;
+SharedKeyDeriver curve25519_derive_shared_key = &null_curve25519_derive_shared_key;
+SharedKeyDeleter curve25519_delete_shared_key = NULL;//&null_curve25519_delete_shared_key;
+Encrypter curve25519_encrypt = NULL;//&null_curve25519_encrypt;
+Deinitializer curve25519_deinitialize = &null_curve25519_deinitialize;
diff --git a/libcmix-crypto/curve25519/sodium/libsodium_curve25519.c b/libcmix-crypto/curve25519/sodium/libsodium_curve25519.c
index 2405442..b4ae963 100644
--- a/libcmix-crypto/curve25519/sodium/libsodium_curve25519.c
+++ b/libcmix-crypto/curve25519/sodium/libsodium_curve25519.c
@@ -6,13 +6,13 @@
 #include <stddef.h>
 #include <stdlib.h>
 
-void curve25519_initialize(void) {
+void sodium_curve25519_initialize(void) {
 	if(sodium_init() == -1) {
 		exit(-1);
 	}
 }
 
-void curve25519_keypair_deleter(struct KeyPair* p) {
+void sodium_curve25519_delete_keypair(struct KeyPair* p) {
 	sodium_free(p->sec);
 	free(p->pub);
 
@@ -20,7 +20,7 @@ void curve25519_keypair_deleter(struct KeyPair* p) {
 	p->pub = NULL;
 }
 
-struct KeyPair curve25519_create_keypair(void) {
+struct KeyPair sodium_curve25519_create_keypair(void) {
 	unsigned char* sec = (unsigned char*) sodium_malloc(crypto_box_SECRETKEYBYTES);
 	unsigned char* pub = (unsigned char*) malloc(crypto_box_PUBLICKEYBYTES);
 
@@ -33,21 +33,21 @@ struct KeyPair curve25519_create_keypair(void) {
 	};
 }
 
-void curve25519_shared_key_deleter(struct SharedKey* s) {
+void sodium_curve25519_shared_key_deleter(struct SharedKey* s) {
 	sodium_free(s->shared);
 
 	s->shared = NULL;
 }
 
-void curve25519_key_to_array(unsigned char** buffer, size_t* len, void* key) {
+void sodium_curve25519_key_to_array(unsigned char** buffer, size_t* len, void* key) {
 
 }
 
-void curve25519_add_public_share(char** buffer, size_t* out_len, char const* share, size_t in_len, void* pubkey) {
+void sodium_curve25519_add_public_share(char** buffer, size_t* out_len, char const* share, size_t in_len, void* pubkey) {
 
 }
 
-GroupElement curve25519_derive_shared_key(struct KeyPair pair, unsigned char const* other_pub, size_t pub_len, unsigned char const* value, size_t value_len, void* priv_value, bool swap_pub_order) {
+GroupElement sodium_curve25519_derive_shared_key(struct KeyPair pair, unsigned char const* other_pub, size_t pub_len, unsigned char const* value, size_t value_len, void* priv_value, bool swap_pub_order) {
 	unsigned char* shared = (unsigned char*) sodium_malloc(crypto_generichash_BYTES);
 
 	crypto_generichash_state h;
@@ -74,5 +74,22 @@ GroupElement curve25519_derive_shared_key(struct KeyPair pair, unsigned char con
 	return shared;
 }
 
-void curve25519_deinitialize(void) {}
-
+void sodium_curve25519_deinitialize(void) {}
+
+Initializer curve25519_initialize = &sodium_curve25519_initialize;
+KeyPairCreator curve25519_create_keypair = &sodium_curve25519_create_keypair;
+KeyPairDeleter curve25519_delete_keypair = &sodium_curve25519_delete_keypair;
+ElementToArray curve25519_element_to_array = NULL;//&sodium_curve25519_element_to_array;
+BufferDeleter curve25519_free_buffer = NULL;//&sodium_curve25519_free_buffer;
+ArrayToElement curve25519_array_to_element = NULL;//&sodium_curve25519_array_to_element;
+GroupElementGetter curve25519_get_group_element = NULL;//&sodium_curve25519_get_group_element;
+GroupElementDeleter curve25519_delete_group_element = NULL;//&sodium_curve25519_delete_group_element;
+KeyExchangeValueGetter curve25519_get_key_exchange_value = NULL;//&sodium_curve25519_get_key_exchange_value;
+GroupElementMultiplier curve25519_multiply = NULL;//&sodium_curve25519_multiply;
+DecryptionShareGetter curve25519_get_decryption_share = NULL;//&sodium_curve25519_get_decryption_share;
+GroupElementArraySizeGetter curve25519_get_group_element_array_size = NULL;//&sodium_curve25519_get_group_element_array_size;
+PublicShareAdder curve25519_add_public_share = NULL;//&sodium_curve25519_add_public_share;
+SharedKeyDeriver curve25519_derive_shared_key = &sodium_curve25519_derive_shared_key;
+SharedKeyDeleter curve25519_delete_shared_key = NULL;//&sodium_curve25519_delete_shared_key;
+Encrypter curve25519_encrypt = NULL;//&sodium_curve25519_encrypt;
+Deinitializer curve25519_deinitialize = &sodium_curve25519_deinitialize;
diff --git a/libcmix-crypto/elgamal/elgamal.c b/libcmix-crypto/elgamal/elgamal.c
index e54f76d..dbfccb9 100644
--- a/libcmix-crypto/elgamal/elgamal.c
+++ b/libcmix-crypto/elgamal/elgamal.c
@@ -15,6 +15,7 @@ struct Api get_elgamal_implementation()
 		.free_group_element = elgamal_delete_group_element,
 		.get_key_exchange_value = elgamal_get_key_exchange_value,
 		.multiply = elgamal_multiply,
+		.get_decryption_share = elgamal_get_decryption_share,
 		.add_public_share = elgamal_add_public_share,
 		.derive_shared_key = elgamal_derive_shared_key,
 		.free_shared_key = elgamal_delete_shared_key,
diff --git a/libcmix-crypto/elgamal/elgamal.h b/libcmix-crypto/elgamal/elgamal.h
index 43ddca0..21bf58a 100644
--- a/libcmix-crypto/elgamal/elgamal.h
+++ b/libcmix-crypto/elgamal/elgamal.h
@@ -30,6 +30,8 @@ extern KeyExchangeValueGetter elgamal_get_key_exchange_value;
 
 extern GroupElementMultiplier elgamal_multiply;
 
+extern DecryptionShareGetter elgamal_get_decryption_share;
+
 extern GroupElementArraySizeGetter elgamal_get_group_element_array_size;
 
 extern PublicShareAdder elgamal_add_public_share;
diff --git a/libcmix-crypto/elgamal/gcrypt/gcrypt_elgamal.c b/libcmix-crypto/elgamal/gcrypt/gcrypt_elgamal.c
index c610556..1824ccc 100644
--- a/libcmix-crypto/elgamal/gcrypt/gcrypt_elgamal.c
+++ b/libcmix-crypto/elgamal/gcrypt/gcrypt_elgamal.c
@@ -152,6 +152,16 @@ GroupElement gcrypt_elgamal_multiply(GroupElement lh, GroupElement rh, bool secu
 	return ret;
 }
 
+GroupElement gcrypt_elgamal_get_decryption_share(GroupElement r, GroupElement e) {
+	gcry_mpi_t inve = gcry_mpi_snew(0);
+	gcry_mpi_invm(inve, (gcry_mpi_t)e, p);
+	
+	gcry_mpi_t d = gcry_mpi_snew(0);
+	gcry_mpi_powm(d, (gcry_mpi_t)r, inve, p);
+	gcry_mpi_release(inve);
+	return d;
+}
+
 size_t gcrypt_elgamal_get_group_element_array_size() {
 	return 256u;
 }
@@ -241,6 +251,7 @@ GroupElementGetter elgamal_get_group_element = &gcrypt_elgamal_get_group_element
 GroupElementDeleter elgamal_delete_group_element = &gcrypt_elgamal_delete_group_element;
 KeyExchangeValueGetter elgamal_get_key_exchange_value = &gcrypt_elgamal_get_key_exchange_value;
 GroupElementMultiplier elgamal_multiply = &gcrypt_elgamal_multiply;
+DecryptionShareGetter elgamal_get_decryption_share = &gcrypt_elgamal_get_decryption_share;
 GroupElementArraySizeGetter elgamal_get_group_element_array_size = &gcrypt_elgamal_get_group_element_array_size;
 PublicShareAdder elgamal_add_public_share = &gcrypt_elgamal_add_public_share;
 SharedKeyDeriver elgamal_derive_shared_key = &gcrypt_elgamal_derive_shared_key;
diff --git a/libcmix-crypto/elgamal/null/null_elgamal.c b/libcmix-crypto/elgamal/null/null_elgamal.c
index 17478e1..2b5c43b 100644
--- a/libcmix-crypto/elgamal/null/null_elgamal.c
+++ b/libcmix-crypto/elgamal/null/null_elgamal.c
@@ -1,30 +1,46 @@
 
-#include "api.h"
+#include "elgamal.h"
 
 #include <stddef.h>
 #include <stdbool.h>
 
-void elgamal_initialize(void) {}
+void null_elgamal_initialize(void) {}
 
-void elgamal_keypair_deleter(struct KeyPair p) {}
+void null_elgamal_keypair_deleter(struct KeyPair p) {}
 
-struct KeyPair elgamal_create_keypair() {
+struct KeyPair null_elgamal_create_keypair() {
 	return (struct KeyPair){
 		NULL,
 		NULL,
 	};
 }
 
-void elgamal_get_key_array(char** buffer, size_t* len, void* pubkey) {}
+void null_elgamal_get_key_array(char** buffer, size_t* len, void* pubkey) {}
 
-void elgamal_add_public_share(char** buffer, size_t* out_len, char const* share, size_t in_len, void* pubkey) {}
+void null_elgamal_add_public_share(char** buffer, size_t* out_len, char const* share, size_t in_len, void* pubkey) {}
 
-struct SharedKey elgamal_derive_shared_key(struct KeyPair pair, void const* pub_key, bool swap_pub_order) {
-	return (struct SharedKey){
-		NULL,
-	};
+GroupElement null_elgamal_derive_shared_key(struct KeyPair keypair, unsigned char const* other_pub, size_t pub_len, unsigned char const* value, size_t value_len, void* priv_value, bool swap) {
+	return NULL;
 }
 
-void elgamal_shared_key_deleter(struct SharedKey* s) {}
-
-void elgamal_deinitialize(void) {}
+void null_elgamal_shared_key_deleter(struct SharedKey* s) {}
+
+void null_elgamal_deinitialize(void) {}
+
+Initializer elgamal_initialize = &null_elgamal_initialize;
+KeyPairCreator elgamal_create_keypair = &null_elgamal_create_keypair;
+KeyPairDeleter elgamal_delete_keypair = NULL;//&null_elgamal_delete_keypair;
+ElementToArray elgamal_element_to_array = NULL;//&null_elgamal_element_to_array;
+BufferDeleter elgamal_free_buffer = NULL;//&null_elgamal_free_buffer;
+ArrayToElement elgamal_array_to_element = NULL;//&null_elgamal_array_to_element;
+GroupElementGetter elgamal_get_group_element = NULL;//&null_elgamal_get_group_element;
+GroupElementDeleter elgamal_delete_group_element = NULL;//&null_elgamal_delete_group_element;
+KeyExchangeValueGetter elgamal_get_key_exchange_value = NULL;//&null_elgamal_get_key_exchange_value;
+GroupElementMultiplier elgamal_multiply = NULL;//&null_elgamal_multiply;
+DecryptionShareGetter elgamal_get_decryption_share = NULL;//&null_elgamal_get_decryption_share;
+GroupElementArraySizeGetter elgamal_get_group_element_array_size = NULL;//&null_elgamal_get_group_element_array_size;
+PublicShareAdder elgamal_add_public_share = NULL;//&null_elgamal_add_public_share;
+SharedKeyDeriver elgamal_derive_shared_key = &null_elgamal_derive_shared_key;
+SharedKeyDeleter elgamal_delete_shared_key = NULL;//&null_elgamal_delete_shared_key;
+Encrypter elgamal_encrypt = NULL;//&null_elgamal_encrypt;
+Deinitializer elgamal_deinitialize = &null_elgamal_deinitialize;
\ No newline at end of file
diff --git a/libcmix-protobuf/cmix.proto b/libcmix-protobuf/cmix.proto
index 00ab377..e048fef 100644
--- a/libcmix-protobuf/cmix.proto
+++ b/libcmix-protobuf/cmix.proto
@@ -40,7 +40,8 @@ message PreMix {
 }
 
 message PrePost {
-	repeated bytes PiRS = 1;
+	repeated bytes r_EPiRS = 1;
+	repeated bytes m_EPiRS = 2;
 }
 
 message CMixMessage {
@@ -54,5 +55,6 @@ message CMixMessage {
 		NodeReady nodeready = 7;
 		PrePre prepre = 8;
 		PreMix premix = 9;
+		PrePost prepost = 10;
 	}
 }
diff --git a/libcmix/cmix.c b/libcmix/cmix.c
index 4893c6c..28f56db 100644
--- a/libcmix/cmix.c
+++ b/libcmix/cmix.c
@@ -216,3 +216,19 @@ enum cmix_error key_exchange(struct CMixContext const* ctx, GroupElement* shared
 	
 	return no_error;
 }
+
+enum cmix_error post_process(struct CMixContext* ctx, char const* r_epirs, char const* m_epirs, size_t index) {
+	GroupElement x = ctx->api.array_to_element(r_epirs, get_group_element_array_size(ctx), true);
+	
+	GroupElement D = ctx->api.get_decryption_share(x, ctx->keypair.sec);
+	
+	GroupElement msg = ctx->api.array_to_element(m_epirs, get_group_element_array_size(ctx), true);
+	GroupElement pirs = ctx->api.multiply(D, msg, true);
+	
+	ctx->pirs[index] = pirs;
+	ctx->api.free_group_element(x);
+	ctx->api.free_group_element(D);
+	ctx->api.free_group_element(msg);
+	
+	return no_error;
+}
diff --git a/libcmix/cmix.h b/libcmix/cmix.h
index 3877382..433c3bc 100644
--- a/libcmix/cmix.h
+++ b/libcmix/cmix.h
@@ -106,6 +106,8 @@ enum cmix_error multiply_s(struct CMixContext const* ctx, char* r_out_buffer, ch
 
 enum cmix_error key_exchange(struct CMixContext const* ctx, GroupElement* shared_key, char* public_key_buffer, char* exhange_value_buffer, char const* pubkey, char const* value);
 
+enum cmix_error post_process(struct CMixContext* ctx, char const* r_epirs, char const* m_epirs, size_t index);
+
 #ifdef __cplusplus
 } // extern "C"
 #endif
diff --git a/node/node.cpp b/node/node.cpp
index 98b5873..a781755 100644
--- a/node/node.cpp
+++ b/node/node.cpp
@@ -115,28 +115,6 @@ void Node::handle_node_secretkey(cmix_proto::SecretKey const& secret)
 }
 
 template <typename T>
-cmix_proto::PreMix fill_precomputation_mix_message(CMixContext const& ctx, T const& rs, T const& ms) {
-	cmix_proto::PreMix premix;
-	for(size_t i = 0; i < ctx.nr_participants; ++i) {
-		auto new_pos = ctx.permutation[i];
-		size_t el_len = get_group_element_array_size(&ctx);
-		
-		premix.mutable_r_epirs(new_pos)->resize(el_len);
-		premix.mutable_m_epirs(new_pos)->resize(el_len);
-		
-		multiply_s(
-			&ctx,
-			&(*premix.mutable_r_epirs(new_pos))[0],
-			&(*premix.mutable_m_epirs(new_pos))[0],
-			rs.Get(i).data(),
-			ms.Get(i).data(),
-			i
-		);
-	}
-	return premix;
-}
-
-template <typename T>
 cmix_proto::PrePre fill_precomputation_pre_message(CMixContext& ctx, T const& rs, T const& ms) {
 	if(start_mix(&ctx, rs.size()) != no_error) {
 		exit(-1);
@@ -148,7 +126,7 @@ cmix_proto::PrePre fill_precomputation_pre_message(CMixContext& ctx, T const& rs
 	
 	cmix_proto::PrePre prepre;
 	
-	for(int i = 0; i < rs.size(); ++i) {
+	for(size_t i = 0; i < ctx.nr_participants; ++i) {
 		size_t len = get_group_element_array_size(&ctx);
 		
 		prepre.mutable_m_er(i)->resize(len);
@@ -168,6 +146,41 @@ cmix_proto::PrePre fill_precomputation_pre_message(CMixContext& ctx, T const& rs
 	return prepre;
 }
 
+template <typename T>
+cmix_proto::PreMix fill_precomputation_mix_message(CMixContext const& ctx, T const& rs, T const& ms) {
+	cmix_proto::PreMix premix;
+	for(size_t i = 0; i < ctx.nr_participants; ++i) {
+		auto new_pos = ctx.permutation[i];
+		size_t el_len = get_group_element_array_size(&ctx);
+		
+		premix.mutable_r_epirs(new_pos)->resize(el_len);
+		premix.mutable_m_epirs(new_pos)->resize(el_len);
+		
+		multiply_s(
+			&ctx,
+			&(*premix.mutable_r_epirs(new_pos))[0],
+			&(*premix.mutable_m_epirs(new_pos))[0],
+			rs.Get(i).data(),
+			ms.Get(i).data(),
+			i
+		);
+	}
+	return premix;
+}
+
+template <typename T>
+cmix_proto::PrePost fill_precomputation_post_message(CMixContext& ctx, T const& rs, T const& ms) {
+	cmix_proto::PrePost prepost;
+	
+	for(size_t i = 0; i < ctx.nr_participants; ++i) {
+		post_process(&ctx, rs.Get(i).data(), ms.Get(i).data(), i);
+		*prepost.mutable_r_epirs(i) = rs.Get(i);
+		*prepost.mutable_m_epirs(i) = ms.Get(i);
+	}
+	
+	return prepost;
+}
+
 void Node::handle_node_prepre(cmix_proto::PrePre const& pre) {
 	if(network_settings.is_first) {
 		cmix_proto::PreMix premix = fill_precomputation_mix_message(cmix_ctx, pre.r_er(), pre.m_er());
@@ -180,13 +193,23 @@ void Node::handle_node_prepre(cmix_proto::PrePre const& pre) {
 
 void Node::handle_node_premix(cmix_proto::PreMix const& premix) {
 	if(network_settings.is_first) {
-		
+		cmix_proto::PrePost prepost = fill_precomputation_post_message(cmix_ctx, premix.r_epirs(), premix.m_epirs());
+		next_node.async_send(prepost);	
 	} else {
 		cmix_proto::PreMix n_premix = fill_precomputation_mix_message(cmix_ctx, premix.r_epirs(), premix.m_epirs());
 		next_node.async_send(n_premix);
 	}
 }
 
+void Node::handle_node_prepost(cmix_proto::PrePost const& prepost) {
+	if(network_settings.is_first) {
+		
+	} else {
+		cmix_proto::PrePost n_prepost = fill_precomputation_post_message(cmix_ctx, prepost.r_epirs(), prepost.m_epirs());
+		next_node.async_send(n_prepost);
+	}
+}
+
 void Node::handle_node_message(cmix_proto::CMixMessage message)
 {
 	switch(message.contents_case()) {
@@ -215,6 +238,11 @@ void Node::handle_node_message(cmix_proto::CMixMessage message)
 			handle_node_premix(message.premix());
 			break;
 		}
+		case cmix_proto::CMixMessage::ContentsCase::kPrepost: {
+			BOOST_LOG_TRIVIAL(trace) << "Handling PrePost";
+			handle_node_prepost(message.prepost());
+			break;
+		}
 		default: {
 			BOOST_LOG_TRIVIAL(error) << "handle_node_message: CMixMessage contains unknown contents.";
 		}
diff --git a/node/node.hpp b/node/node.hpp
index 6587556..a143359 100644
--- a/node/node.hpp
+++ b/node/node.hpp
@@ -83,6 +83,7 @@ class Node
 	void handle_node_secretkey(cmix_proto::SecretKey const& secret);
 	void handle_node_prepre(cmix_proto::PrePre const& prepre);
 	void handle_node_premix(cmix_proto::PreMix const& premix);
+	void handle_node_prepost(cmix_proto::PrePost const& prepost);
 	void handle_node_message(cmix_proto::CMixMessage message);
 	
 	void handle_client_keyexchange(ClientConnections::key_type handle, cmix_proto::KeyExchange ke);