Migrated first 6 gists.

rc4.c/README.md

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+Backup of the RC4 algorithm implementation from https://web.archive.org/web/20080404222417/http://cypherpunks.venona.com/date/1994/09/msg00304.html

rc4.c/rc4.c

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+/*rc4.c */
+
+#include "rc4.h"
+
+static void swap_byte(unsigned char *a, unsigned char *b);
+
+void prepare_key(unsigned char *key_data_ptr, int key_data_len, rc4_key *key)
+{
+     unsigned char swapByte;
+     unsigned char index1;
+     unsigned char index2;
+     unsigned char* state;
+     short counter;     
+     
+     state = &key->state[0];         
+     for(counter = 0; counter < 256; counter++)              
+     state[counter] = counter;               
+     key->x = 0;     
+     key->y = 0;     
+     index1 = 0;     
+     index2 = 0;             
+     for(counter = 0; counter < 256; counter++)      
+     {               
+          index2 = (key_data_ptr[index1] + state[counter] + index2) % 256;                
+          swap_byte(&state[counter], &state[index2]);
+
+          index1 = (index1 + 1) % key_data_len;
+     }       
+ }
+ 
+ void rc4(unsigned char *buffer_ptr, int buffer_len, rc4_key *key)
+ { 
+     unsigned char x;
+     unsigned char y;
+     unsigned char* state;
+     unsigned char xorIndex;
+     short counter;              
+     
+     x = key->x;     
+     y = key->y;     
+     
+     state = &key->state[0];         
+     for(counter = 0; counter < buffer_len; counter ++)      
+     {               
+          x = (x + 1) % 256;                      
+          y = (state[x] + y) % 256;               
+          swap_byte(&state[x], &state[y]);                        
+
+          xorIndex = state[x] + (state[y]) % 256;                 
+
+          buffer_ptr[counter] ^= state[xorIndex];         
+      }               
+      key->x = x;     
+      key->y = y;
+ }
+ 
+ static void swap_byte(unsigned char *a, unsigned char *b)
+ {
+     unsigned char swapByte; 
+     
+     swapByte = *a; 
+     *a = *b;      
+     *b = swapByte;
+ }

rc4.c/rc4.h

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+/* rc4.h */
+
+typedef struct rc4_key
+{      
+     unsigned char state[256];       
+     unsigned char x;        
+     unsigned char y;
+} rc4_key;
+
+void prepare_key(unsigned char *key_data_ptr,int key_data_len, rc4_key *key);
+
+void rc4(unsigned char *buffer_ptr,int buffer_len,rc4_key * key);