Implemented encrypt_data_fast, decrypt_data_fast and crypto tests

7 files changed, 340 insertions, 21 deletions

diff --git a/auto_tests/CMakeLists.txt b/auto_tests/CMakeLists.txt
index fbbcb7d7..c0b6aee4 100644
--- a/auto_tests/CMakeLists.txt
+++ b/auto_tests/CMakeLists.txt
@@ -5,16 +5,18 @@ include_directories(${CHECK_INCLUDE_DIRS})
 
 find_package(Check REQUIRED)
 include(${CMAKE_CURRENT_SOURCE_DIR}/cmake/messenger_test.cmake)
+include(${CMAKE_CURRENT_SOURCE_DIR}/cmake/crypto_test.cmake)
 include(${CMAKE_CURRENT_SOURCE_DIR}/cmake/friends_test.cmake)
 
 include( CTest )
 enable_testing()
 
 add_test(messenger messenger_test)
+add_test(crypto crypto_test)
 # TODO enable once test is fixed
 #add_test(friends friends_test)
 
 add_custom_target(
     test COMMAND ${CMAKE_CTEST_COMMAND} -V 
-    DEPENDS messenger_test
+    DEPENDS messenger_test crypto_test
 )
diff --git a/auto_tests/cmake/crypto_test.cmake b/auto_tests/cmake/crypto_test.cmake
new file mode 100644
index 00000000..9ca9a331
--- /dev/null
+++ b/auto_tests/cmake/crypto_test.cmake
@@ -0,0 +1,10 @@
+cmake_minimum_required(VERSION 2.6.0)
+project(crypto_test C)
+set(exe_name crypto_test)
+
+add_executable(${exe_name}
+    crypto_test.c)
+
+linkCoreLibraries(${exe_name})
+add_dependencies(${exe_name} Check)
+target_link_libraries(${exe_name} check)
diff --git a/auto_tests/crypto_test.c b/auto_tests/crypto_test.c
new file mode 100644
index 00000000..9ac81349
--- /dev/null
+++ b/auto_tests/crypto_test.c
@@ -0,0 +1,230 @@
+#include "../core/net_crypto.h"
+#include <sys/types.h>
+#include <stdint.h>
+#include <string.h>
+#include <check.h>
+#include <stdlib.h>
+#include <time.h>
+#include <sodium.h>
+
+void rand_bytes(uint8_t *b, size_t blen)
+{
+    size_t i;
+    for (i = 0; i < blen; i++)
+    {
+        b[i] = rand();
+    }
+}
+
+// These test vectors are from libsodium's test suite
+
+unsigned char alicesk[32] = {
+    0x77,0x07,0x6d,0x0a,0x73,0x18,0xa5,0x7d,
+    0x3c,0x16,0xc1,0x72,0x51,0xb2,0x66,0x45,
+    0xdf,0x4c,0x2f,0x87,0xeb,0xc0,0x99,0x2a,
+    0xb1,0x77,0xfb,0xa5,0x1d,0xb9,0x2c,0x2a
+};
+
+unsigned char bobpk[32] = {
+    0xde,0x9e,0xdb,0x7d,0x7b,0x7d,0xc1,0xb4,
+    0xd3,0x5b,0x61,0xc2,0xec,0xe4,0x35,0x37,
+    0x3f,0x83,0x43,0xc8,0x5b,0x78,0x67,0x4d,
+    0xad,0xfc,0x7e,0x14,0x6f,0x88,0x2b,0x4f
+};
+
+unsigned char nonce[24] = {
+    0x69,0x69,0x6e,0xe9,0x55,0xb6,0x2b,0x73,
+    0xcd,0x62,0xbd,0xa8,0x75,0xfc,0x73,0xd6,
+    0x82,0x19,0xe0,0x03,0x6b,0x7a,0x0b,0x37
+};
+
+unsigned char test_m[131] = {
+    0xbe,0x07,0x5f,0xc5,0x3c,0x81,0xf2,0xd5,
+    0xcf,0x14,0x13,0x16,0xeb,0xeb,0x0c,0x7b,
+    0x52,0x28,0xc5,0x2a,0x4c,0x62,0xcb,0xd4,
+    0x4b,0x66,0x84,0x9b,0x64,0x24,0x4f,0xfc,
+    0xe5,0xec,0xba,0xaf,0x33,0xbd,0x75,0x1a,
+    0x1a,0xc7,0x28,0xd4,0x5e,0x6c,0x61,0x29,
+    0x6c,0xdc,0x3c,0x01,0x23,0x35,0x61,0xf4,
+    0x1d,0xb6,0x6c,0xce,0x31,0x4a,0xdb,0x31,
+    0x0e,0x3b,0xe8,0x25,0x0c,0x46,0xf0,0x6d,
+    0xce,0xea,0x3a,0x7f,0xa1,0x34,0x80,0x57,
+    0xe2,0xf6,0x55,0x6a,0xd6,0xb1,0x31,0x8a,
+    0x02,0x4a,0x83,0x8f,0x21,0xaf,0x1f,0xde,
+    0x04,0x89,0x77,0xeb,0x48,0xf5,0x9f,0xfd,
+    0x49,0x24,0xca,0x1c,0x60,0x90,0x2e,0x52,
+    0xf0,0xa0,0x89,0xbc,0x76,0x89,0x70,0x40,
+    0xe0,0x82,0xf9,0x37,0x76,0x38,0x48,0x64,
+    0x5e,0x07,0x05
+};
+
+unsigned char test_c[147] = {
+    0xf3,0xff,0xc7,0x70,0x3f,0x94,0x00,0xe5,
+    0x2a,0x7d,0xfb,0x4b,0x3d,0x33,0x05,0xd9,
+    0x8e,0x99,0x3b,0x9f,0x48,0x68,0x12,0x73,
+    0xc2,0x96,0x50,0xba,0x32,0xfc,0x76,0xce,
+    0x48,0x33,0x2e,0xa7,0x16,0x4d,0x96,0xa4,
+    0x47,0x6f,0xb8,0xc5,0x31,0xa1,0x18,0x6a,
+    0xc0,0xdf,0xc1,0x7c,0x98,0xdc,0xe8,0x7b,
+    0x4d,0xa7,0xf0,0x11,0xec,0x48,0xc9,0x72,
+    0x71,0xd2,0xc2,0x0f,0x9b,0x92,0x8f,0xe2,
+    0x27,0x0d,0x6f,0xb8,0x63,0xd5,0x17,0x38,
+    0xb4,0x8e,0xee,0xe3,0x14,0xa7,0xcc,0x8a,
+    0xb9,0x32,0x16,0x45,0x48,0xe5,0x26,0xae,
+    0x90,0x22,0x43,0x68,0x51,0x7a,0xcf,0xea,
+    0xbd,0x6b,0xb3,0x73,0x2b,0xc0,0xe9,0xda,
+    0x99,0x83,0x2b,0x61,0xca,0x01,0xb6,0xde,
+    0x56,0x24,0x4a,0x9e,0x88,0xd5,0xf9,0xb3,
+    0x79,0x73,0xf6,0x22,0xa4,0x3d,0x14,0xa6,
+    0x59,0x9b,0x1f,0x65,0x4c,0xb4,0x5a,0x74,
+    0xe3,0x55,0xa5
+};
+
+START_TEST(test_known)
+{
+    unsigned char c[147];
+    unsigned char m[131];
+    int clen, mlen;
+
+    ck_assert_msg(sizeof(c) == sizeof(m) + ENCRYPTION_PADDING * sizeof(unsigned char), "cyphertext should be ENCRYPTION_PADDING bytes longer than plaintext");
+    ck_assert_msg(sizeof(test_c) == sizeof(c), "sanity check failed");
+    ck_assert_msg(sizeof(test_m) == sizeof(m), "sanity check failed");
+
+    clen = encrypt_data(bobpk, alicesk, nonce, test_m, sizeof(test_m)/sizeof(unsigned char), c);
+
+    ck_assert_msg(memcmp(test_c, c, sizeof(c)) == 0, "cyphertext doesn't match test vector");
+    ck_assert_msg(clen == sizeof(c)/sizeof(unsigned char), "wrong ciphertext length");
+
+    mlen = decrypt_data(bobpk, alicesk, nonce, test_c, sizeof(test_c)/sizeof(unsigned char), m);
+
+    ck_assert_msg(memcmp(test_m, m, sizeof(m)) == 0, "decrypted text doesn't match test vector");
+    ck_assert_msg(mlen == sizeof(m)/sizeof(unsigned char), "wrong plaintext length");
+}
+END_TEST
+
+START_TEST(test_fast_known)
+{
+    unsigned char k[crypto_box_BEFORENMBYTES];
+    unsigned char c[147];
+    unsigned char m[131];
+    int clen, mlen;
+
+    encrypt_precompute(bobpk, alicesk, k);
+
+    ck_assert_msg(sizeof(c) == sizeof(m) + ENCRYPTION_PADDING * sizeof(unsigned char), "cyphertext should be ENCRYPTION_PADDING bytes longer than plaintext");
+    ck_assert_msg(sizeof(test_c) == sizeof(c), "sanity check failed");
+    ck_assert_msg(sizeof(test_m) == sizeof(m), "sanity check failed");
+
+    clen = encrypt_data_fast(k, nonce, test_m, sizeof(test_m)/sizeof(unsigned char), c);
+
+    ck_assert_msg(memcmp(test_c, c, sizeof(c)) == 0, "cyphertext doesn't match test vector");
+    ck_assert_msg(clen == sizeof(c)/sizeof(unsigned char), "wrong ciphertext length");
+
+    mlen = decrypt_data_fast(k, nonce, test_c, sizeof(test_c)/sizeof(unsigned char), m);
+
+    ck_assert_msg(memcmp(test_m, m, sizeof(m)) == 0, "decrypted text doesn't match test vector");
+    ck_assert_msg(mlen == sizeof(m)/sizeof(unsigned char), "wrong plaintext length");
+   
+}
+END_TEST
+
+START_TEST(test_endtoend)
+{
+    unsigned char pk1[crypto_box_PUBLICKEYBYTES];
+    unsigned char sk1[crypto_box_SECRETKEYBYTES];
+    unsigned char pk2[crypto_box_PUBLICKEYBYTES];
+    unsigned char sk2[crypto_box_SECRETKEYBYTES];
+    unsigned char k1[crypto_box_BEFORENMBYTES];
+    unsigned char k2[crypto_box_BEFORENMBYTES];
+
+    unsigned char n[crypto_box_NONCEBYTES];
+
+    unsigned char m[500];
+    unsigned char c1[sizeof(m) + ENCRYPTION_PADDING];
+    unsigned char c2[sizeof(m) + ENCRYPTION_PADDING];
+    unsigned char c3[sizeof(m) + ENCRYPTION_PADDING];
+    unsigned char c4[sizeof(m) + ENCRYPTION_PADDING];
+    unsigned char m1[sizeof(m)];
+    unsigned char m2[sizeof(m)];
+    unsigned char m3[sizeof(m)];
+    unsigned char m4[sizeof(m)];
+
+    int mlen;
+    int c1len, c2len, c3len, c4len;
+    int m1len, m2len, m3len, m4len;
+
+    int testno;
+
+    // Test 100 random messages and keypairs
+    for (testno = 0; testno < 100; testno++)
+    {
+        //Generate random message (random length from 100 to 500)
+        mlen = (rand() % 400) + 100;
+        rand_bytes(m, mlen);
+        rand_bytes(n, crypto_box_NONCEBYTES);
+        
+        //Generate keypairs
+        crypto_box_keypair(pk1,sk1);
+        crypto_box_keypair(pk2,sk2);
+        
+        //Precompute shared keys
+        encrypt_precompute(pk2, sk1, k1);
+        encrypt_precompute(pk1, sk2, k2);
+        
+        ck_assert_msg(memcmp(k1, k2, crypto_box_BEFORENMBYTES) == 0, "encrypt_precompute: bad");
+        
+        //Encrypt all four ways
+        c1len = encrypt_data(pk2, sk1, n, m, mlen, c1);
+        c2len = encrypt_data(pk1, sk2, n, m, mlen, c2);
+        c3len = encrypt_data_fast(k1, n, m, mlen, c3);
+        c4len = encrypt_data_fast(k2, n, m, mlen, c4);
+
+        ck_assert_msg(c1len == c2len && c1len == c3len && c1len == c4len, "cyphertext lengths differ");
+        ck_assert_msg(c1len == mlen + ENCRYPTION_PADDING, "wrong cyphertext length");
+        ck_assert_msg(memcmp(c1, c2, c1len) == 0 && memcmp(c1, c3, c1len) == 0 && memcmp(c1, c4, c1len) == 0, "crypertexts differ");
+
+        //Decrypt all four ways
+        m1len = decrypt_data(pk2, sk1, n, c1, c1len, m1);
+        m2len = decrypt_data(pk1, sk2, n, c1, c1len, m2);
+        m3len = decrypt_data_fast(k1, n, c1, c1len, m3);
+        m4len = decrypt_data_fast(k2, n, c1, c1len, m4);
+
+        ck_assert_msg(m1len == m2len && m1len == m3len && m1len == m4len, "decrypted text lengths differ");
+        ck_assert_msg(m1len == mlen, "wrong decrypted text length");
+        ck_assert_msg(memcmp(m1, m2, mlen) == 0 && memcmp(m1, m3, mlen) == 0 && memcmp(m1, m4, mlen) == 0, "decrypted texts differ");
+        ck_assert_msg(memcmp(m1, m, mlen) == 0, "wrong decrypted text");
+    }
+}
+END_TEST
+
+#define DEFTESTCASE(NAME) \
+    TCase *NAME = tcase_create(#NAME); \
+    tcase_add_test(NAME, test_##NAME); \
+    suite_add_tcase(s, NAME);
+
+Suite* crypto_suite(void)
+{
+    Suite *s = suite_create("Crypto");
+
+    DEFTESTCASE(known);
+    DEFTESTCASE(fast_known);
+    DEFTESTCASE(endtoend);
+
+    return s;
+}
+
+int main(int argc, char* argv[])
+{
+    srand((unsigned int) time(NULL));
+
+    Suite *crypto = crypto_suite();
+    SRunner *test_runner = srunner_create(crypto);
+    int number_failed = 0;
+
+    srunner_run_all(test_runner, CK_NORMAL);
+    number_failed = srunner_ntests_failed(test_runner);
+
+    srunner_free(test_runner);
+
+    return number_failed;
+}
diff --git a/auto_tests/run_tests b/auto_tests/run_tests
index 4448b2e2..1899f354 100755
--- a/auto_tests/run_tests
+++ b/auto_tests/run_tests
@@ -2,4 +2,4 @@
 # run_tests - run the current tests for tox core
 set -e
 
-./messenger_test && ./friends_test 
+./messenger_test && ./friends_test && ./crypto_test
diff --git a/core/net_crypto.c b/core/net_crypto.c
index 1c56b95a..1803caba 100644
--- a/core/net_crypto.c
+++ b/core/net_crypto.c
@@ -37,6 +37,7 @@ typedef struct {
     uint8_t sessionpublic_key[crypto_box_PUBLICKEYBYTES]; /* our public key for this session. */
     uint8_t sessionsecret_key[crypto_box_SECRETKEYBYTES]; /* our private key for this session. */
     uint8_t peersessionpublic_key[crypto_box_PUBLICKEYBYTES]; /* The public key of the peer. */
+    uint8_t shared_key[crypto_box_BEFORENMBYTES]; /* the precomputed shared key from encrypt_precompute */
     uint8_t status; /* 0 if no connection, 1 we have sent a handshake, 2 if connexion is not confirmed yet
                        (we have received a handshake but no empty data packet), 3 if the connection is established.
                        4 if the connection is timed out. */
@@ -59,6 +60,17 @@ static Crypto_Connection crypto_connections[MAX_CRYPTO_CONNECTIONS];
 /* keeps track of the connection numbers for friends request so we can check later if they were sent */
 static int incoming_connections[MAX_INCOMING];
 
+/* Use this instead of memcmp; not vulnerable to timing attacks. */
+uint8_t crypto_iszero(uint8_t *mem, uint32_t length)
+{
+    uint8_t check = 0;
+    uint32_t i;
+    for (i = 0; i < length; ++i) {
+        check |= mem[i];
+    }
+    return check; // We return zero if mem is made out of zeroes.
+}
+
 /* encrypts plain of length length to encrypted of length + 16 using the
    public key(32 bytes) of the receiver and the secret key of the sender and a 24 byte nonce
    return -1 if there was a problem.
@@ -78,12 +90,38 @@ int encrypt_data(uint8_t *public_key, uint8_t *secret_key, uint8_t *nonce,
 
     /* if encryption is successful the first crypto_box_BOXZEROBYTES of the message will be zero
        apparently memcmp should not be used so we do this instead:*/
-    uint32_t i;
-    uint32_t check = 0;
-    for(i = 0; i < crypto_box_BOXZEROBYTES; ++i) {
-            check |= temp_encrypted[i] ^ 0;
-    }
-    if(check != 0)
+    if(crypto_iszero(temp_encrypted, crypto_box_BOXZEROBYTES) != 0)
+        return -1;
+
+    /* unpad the encrypted message */
+    memcpy(encrypted, temp_encrypted + crypto_box_BOXZEROBYTES, length + crypto_box_MACBYTES);
+    return length - crypto_box_BOXZEROBYTES + crypto_box_ZEROBYTES;
+}
+
+/* Precomputes the shared key from their public_key and our secret_key.
+   This way we can avoid an expensive elliptic curve scalar multiply for each 
+   encrypt/decrypt operation.
+   enc_key has to be crypto_box_BEFORENMBYTES bytes long. */
+void encrypt_precompute(uint8_t *public_key, uint8_t *secret_key, uint8_t *enc_key)
+{
+    crypto_box_beforenm(enc_key, public_key, secret_key);
+}
+
+/* Fast encrypt. Depends on enc_key from encrypt_precompute. */
+int encrypt_data_fast(uint8_t *enc_key, uint8_t *nonce, 
+                      uint8_t *plain, uint32_t length, uint8_t *encrypted)
+{
+    if (length + crypto_box_MACBYTES > MAX_DATA_SIZE || length == 0)
+        return -1;
+
+    uint8_t temp_plain[MAX_DATA_SIZE + crypto_box_BOXZEROBYTES] = {0};
+    uint8_t temp_encrypted[MAX_DATA_SIZE + crypto_box_BOXZEROBYTES];
+
+    memcpy(temp_plain + crypto_box_ZEROBYTES, plain, length); /* pad the message with 32 0 bytes. */
+
+    crypto_box_afternm(temp_encrypted, temp_plain, length + crypto_box_ZEROBYTES, nonce, enc_key);
+
+    if(crypto_iszero(temp_encrypted, crypto_box_BOXZEROBYTES) != 0)
         return -1;
 
     /* unpad the encrypted message */
@@ -112,12 +150,33 @@ int decrypt_data(uint8_t *public_key, uint8_t *secret_key, uint8_t *nonce,
 
     /* if decryption is successful the first crypto_box_ZEROBYTES of the message will be zero 
        apparently memcmp should not be used so we do this instead:*/
-    uint32_t i;
-    uint32_t check = 0;
-    for(i = 0; i < crypto_box_ZEROBYTES; ++i) {
-            check |= temp_plain[i] ^ 0;
-    }
-    if(check != 0)
+    if(crypto_iszero(temp_plain, crypto_box_ZEROBYTES) != 0)
+        return -1;
+
+    /* unpad the plain message */
+    memcpy(plain, temp_plain + crypto_box_ZEROBYTES, length - crypto_box_MACBYTES);
+    return length - crypto_box_ZEROBYTES + crypto_box_BOXZEROBYTES;
+}
+
+/* Fast decrypt. Depends on enc_ley from encrypt_precompute. */
+int decrypt_data_fast(uint8_t *enc_key, uint8_t *nonce,
+                      uint8_t *encrypted, uint32_t length, uint8_t *plain)
+{
+    if (length > MAX_DATA_SIZE || length <= crypto_box_BOXZEROBYTES)
+        return -1;
+
+    uint8_t temp_plain[MAX_DATA_SIZE + crypto_box_BOXZEROBYTES];
+    uint8_t temp_encrypted[MAX_DATA_SIZE + crypto_box_BOXZEROBYTES] = {0};
+
+    memcpy(temp_encrypted + crypto_box_BOXZEROBYTES, encrypted, length); /* pad the message with 16 0 bytes. */
+
+    if (crypto_box_open_afternm(temp_plain, temp_encrypted, length + crypto_box_BOXZEROBYTES,
+                                nonce, enc_key) == -1)
+        return -1;
+
+    /* if decryption is successful the first crypto_box_ZEROBYTES of the message will be zero 
+       apparently memcmp should not be used so we do this instead:*/
+    if(crypto_iszero(temp_plain, crypto_box_ZEROBYTES) != 0)
         return -1;
 
     /* unpad the plain message */
@@ -161,9 +220,9 @@ int read_cryptpacket(int crypt_connection_id, uint8_t *data)
         return 0;
     if (temp_data[0] != 3)
         return -1;
-    int len = decrypt_data(crypto_connections[crypt_connection_id].peersessionpublic_key,
-                           crypto_connections[crypt_connection_id].sessionsecret_key,
-                           crypto_connections[crypt_connection_id].recv_nonce, temp_data + 1, length - 1, data);
+    int len = decrypt_data_fast(crypto_connections[crypt_connection_id].shared_key,
+                                crypto_connections[crypt_connection_id].recv_nonce, 
+                                temp_data + 1, length - 1, data);
     if (len != -1) {
         increment_nonce(crypto_connections[crypt_connection_id].recv_nonce);
         return len;
@@ -182,9 +241,9 @@ int write_cryptpacket(int crypt_connection_id, uint8_t *data, uint32_t length)
     if (crypto_connections[crypt_connection_id].status != CONN_ESTABLISHED)
         return 0;
     uint8_t temp_data[MAX_DATA_SIZE];
-    int len = encrypt_data(crypto_connections[crypt_connection_id].peersessionpublic_key,
-                           crypto_connections[crypt_connection_id].sessionsecret_key,
-                           crypto_connections[crypt_connection_id].sent_nonce, data, length, temp_data + 1);
+    int len = encrypt_data_fast(crypto_connections[crypt_connection_id].shared_key,
+                                crypto_connections[crypt_connection_id].sent_nonce, 
+                                data, length, temp_data + 1);
     if (len == -1)
         return 0;
     temp_data[0] = 3;
@@ -408,6 +467,7 @@ int accept_crypto_inbound(int connection_id, uint8_t *public_key, uint8_t *secre
             random_nonce(crypto_connections[i].recv_nonce);
             memcpy(crypto_connections[i].sent_nonce, secret_nonce, crypto_box_NONCEBYTES);
             memcpy(crypto_connections[i].peersessionpublic_key, session_key, crypto_box_PUBLICKEYBYTES);
+            
             increment_nonce(crypto_connections[i].sent_nonce);
             memcpy(crypto_connections[i].public_key, public_key, crypto_box_PUBLICKEYBYTES);
 
@@ -509,6 +569,7 @@ static void receive_crypto(void)
                     if (memcmp(public_key, crypto_connections[i].public_key, crypto_box_PUBLICKEYBYTES) == 0) {
                         memcpy(crypto_connections[i].sent_nonce, secret_nonce, crypto_box_NONCEBYTES);
                         memcpy(crypto_connections[i].peersessionpublic_key, session_key, crypto_box_PUBLICKEYBYTES);
+                        encrypt_precompute(crypto_connections[i].peersessionpublic_key, crypto_connections[i].sessionsecret_key, crypto_connections[i].shared_key);
                         increment_nonce(crypto_connections[i].sent_nonce);
                         uint32_t zero = 0;
                         crypto_connections[i].status = CONN_ESTABLISHED; /* connection status needs to be 3 for write_cryptpacket() to work */
diff --git a/core/net_crypto.h b/core/net_crypto.h
index 66634d45..135e099d 100644
--- a/core/net_crypto.h
+++ b/core/net_crypto.h
@@ -36,6 +36,9 @@ extern uint8_t self_secret_key[crypto_box_SECRETKEYBYTES];
 
 #define ENCRYPTION_PADDING (crypto_box_ZEROBYTES - crypto_box_BOXZEROBYTES)
 
+/* returns zero if the buffer contains only zeros */
+uint8_t crypto_iszero(uint8_t* buffer, uint32_t blen);
+
 /* encrypts plain of length length to encrypted of length + 16 using the
     public key(32 bytes) of the receiver and the secret key of the sender and a 24 byte nonce
     return -1 if there was a problem.
@@ -51,6 +54,19 @@ int encrypt_data(uint8_t *public_key, uint8_t *secret_key, uint8_t *nonce,
 int decrypt_data(uint8_t *public_key, uint8_t *secret_key, uint8_t *nonce,
                     uint8_t *encrypted, uint32_t length, uint8_t *plain);
 
+/* Fast encrypt/decrypt operations. Use if this is not a one-time communication. 
+   encrypt_precompute does the shared-key generation once so it does not have
+   to be preformed on every encrypt/decrypt. */
+void encrypt_precompute(uint8_t *public_key, uint8_t *secret_key, uint8_t *enc_key);
+
+/* Fast encrypt. Depends on enc_key from encrypt_precompute. */
+int encrypt_data_fast(uint8_t *enc_key, uint8_t *nonce, 
+                      uint8_t *plain, uint32_t length, uint8_t *encrypted);
+
+/* Fast decrypt. Depends on enc_ley from encrypt_precompute. */
+int decrypt_data_fast(uint8_t *enc_key, uint8_t *nonce,
+                      uint8_t *encrypted, uint32_t length, uint8_t *plain);
+
 
 /* fill the given nonce with random bytes. */
 void random_nonce(uint8_t *nonce);
diff --git a/other/CMakeLists.txt b/other/CMakeLists.txt
index 05b24f06..db742e3e 100644
--- a/other/CMakeLists.txt
+++ b/other/CMakeLists.txt
@@ -4,6 +4,6 @@ cmake_policy(SET CMP0011 NEW)
 
 include(${CMAKE_CURRENT_SOURCE_DIR}/cmake/DHT_bootstrap.cmake)
 
-if(NOT WIN32)
+if(LINUX)
         add_subdirectory(bootstrap_serverdaemon)
 endif()