diff --git a/server/src/crypto/cipher.cpp b/server/src/crypto/cipher.cpp
index c1bb66a..3d85299 100644
--- a/server/src/crypto/cipher.cpp
+++ b/server/src/crypto/cipher.cpp
@@ -1 +1,45 @@
 #include "cipher.hpp"
+
+template<typename T>
+static void _swap(T& a, T& b) {
+    T tmp = a;
+    a = b;
+    b = tmp;
+}
+
+sosc::cgc::Cipher::Cipher(const KeyExchange& key) {
+    std::string key_raw 
+        = key.GetPrivateKey().ToRawString(key.key_size_bytes);
+        
+    this->state = std::string(256, 0);
+    for(int i = 0; i < this->state_size; ++i)
+        this->state[i] = i;
+    
+    int i = 0, j = 0;
+    for(i = 0; i < this->state_size; ++i)
+        j = (j + this->state[i] + key_raw[i % key_raw.length()]) % 256;
+    
+    GenerateStream(1024);
+}
+
+void sosc::cgc::Cipher::Parse(std::string* data) {
+    std::string stream = this->GenerateStream(data->length());
+    for(std::string::size_type i = 0; i < data->length(); ++i)
+        (*data)[i] ^= stream[i];
+}
+
+std::string sosc::cgc::Cipher::GenerateStream(uint64_t length) {
+    std::string stream(length, 0);
+    int i = 0, j = 0;
+    
+    for(uint64_t x = 0; x < length; ++x) {
+        i = (i + 1) % 256;
+        j = (j + this->state[i]) % 256;
+        _swap(this->state[i], this->state[j]);
+        
+        stream[x] = 
+            this->state[(this->state[i] + this->state[j]) % 256];
+    }
+    
+    return stream;
+}
diff --git a/server/src/crypto/cipher.hpp b/server/src/crypto/cipher.hpp
index dc2ec9a..99d1a81 100644
--- a/server/src/crypto/cipher.hpp
+++ b/server/src/crypto/cipher.hpp
@@ -2,17 +2,19 @@
 #define SOSC_CRYPTO_CIPHER_H
 
 #include "../utils/bigint.hpp"
+#include "keyex.hpp"
 
 namespace sosc {
 namespace cgc {
 class Cipher {
 public:
+    Cipher(const KeyExchange& key);
     
+    void Parse(std::string* data);
 private:
-    const std::string sigma = "expand 32-byte k";
-    const std::string tau = "expand 16-byte k";
+    std::string GenerateStream(uint64_t length);
     
-    std::string key;
+    const int state_size = 256;
     std::string state;
 };
 }}
diff --git a/server/src/crypto/keyex.hpp b/server/src/crypto/keyex.hpp
index b4708eb..bbed485 100644
--- a/server/src/crypto/keyex.hpp
+++ b/server/src/crypto/keyex.hpp
@@ -14,17 +14,17 @@ public:
     bool ParseRequest(const Packet& request, Packet* response);
     bool ParseResponse(const Packet& response);
     
-    inline bool Succeeded() {
+    inline bool Succeeded() const {
         return !this->private_key.IsZero();
     }
     
-    inline const BigUInt& GetPrivateKey() {
+    inline const BigUInt& GetPrivateKey() const {
         return this->private_key;
     }
-private:
-    const int key_size = 256;
-    const int key_size_bytes = key_size / 8;
     
+    const int key_size = 512;
+    const int key_size_bytes = key_size / 8;
+private:
     const BigUInt generator = BigUInt(2u);
     static BigUInt secret;
     BigUInt modulus;
diff --git a/server/src/utils/bigint.cpp b/server/src/utils/bigint.cpp
index cc7eac2..0983f3d 100644
--- a/server/src/utils/bigint.cpp
+++ b/server/src/utils/bigint.cpp
@@ -438,8 +438,14 @@ sosc::BigUInt sosc::BigUInt::operator << (const uint64_t& rhs) const {
 }
 
 std::string sosc::BigUInt::ToRawString(uint64_t byte_count) const {
-    std::string raw(byte_count == 0 ? this->UsedByteCount() : byte_count, 0);
+    uint64_t used_bytes = this->UsedByteCount();
+    byte_count = byte_count == 0 ? used_bytes : byte_count;
+    std::string raw(byte_count, 0);
     
+    for(uint64_t i = 0; i < std::min(byte_count, used_bytes); ++i)
+        raw[i] = (this->value[i / 4] >> (8 * (i % 4))) & 0xFF;
+    
+    return raw;
 }
 
 std::string sosc::BigUInt::ToString() const {