new version using combined PRNGs seeded with 160bit key as key stream

README.md

@@ -1,11 +1,12 @@
-## TWENTY4 - a fun stream cipher
+## TWENTY4/160 - a fun stream cipher
 
 *THIS IS JUST FOR LEARINING CRYPTO, DO NOT EVER USE THIS FOR ANYTHING*
 
-This is the implementation of the fun stream cipher TWENTY4 by T.v. Dein, 09/2015.
+This is the implementation of the fun stream cipher TWENTY4/160 by T.v. Dein, 09/2015.
 Published under the public domain, Creative Commons Zero License. It works bytewise,
-with keys between 1-256 bits in 17 rounds, uses S-Boxes and key output-feedback mode.
-The cipher also works with CBC or ECB mode (sample CBC implementation included).
+uses a 160 bit key bits in 8 rounds, applies an S-Box. From the key various PRNGs
+are seeded, all those PRNGs are recombined into an output key stream, which is being
+xored with the input (after applying of the sbox).
 
 The name TWENTY4 is a reference to article 20 paragraph 4 of the german constitution
 which reads:
@@ -14,7 +15,7 @@ which reads:
 > abolish this constitutional order, if no other remedy is available.
 
 Also, the cipher uses the contents of the german constitution as the source for its
-S-Boxes.
+S-Box.
 
 ## S-Box generation
 
@@ -54,72 +55,16 @@ TWENTY4 uses two S-Box arrays, one for key expansion and one for encryption.
 
 ## Key expansion
 
-The input key will be expanded into a 32 byte array. Maximum key size is
-32 bytes (256 bit).
-
-    IV = KU[0]
-    for ROUND in 0..31
-      if KU[ROUND]
-        K[ROUND] = IV xor KU[ROUND]
-      else
-        K[ROUND] = IV yor KBOX[ROUND * 8];
-      endif
-      K[ROUND] = KBOX[K[ROUND]]
-      IV = K[ROUND]
-    endfor
-    
-    for KROUND in 0..31
-      for ROUND in 0..31
-        K[ROUND] = IV xor (rotateleft(K[ROUND], 3) xor KBOX[rcon(IV)])
-        IV = K[ROUND]
-      endfor
-    endfor
-
-where:
-
-    KU: input key
-    K[17]: initial round key array
-    ROUND: encryption round 1-32
-    KROUND: key expansion round 1-32
-    KBOX[256]: pre computed S-Box for key expansion
+FIXME.
 
 ## Encryption
 
-    for INBYTE in <INSTREAM>
-      OUTBYTE = INBYTE
-      for ROUND in 0..17
-        OUTBYTE = OUTBYTE xor K[ROUND]
-        OUTBYTE = OUTBYTE xor SBOX[OUTBYTE]
-        OUTBYTE = rotateleft(OUTBYTE, ROUND mod 8)
-        OUTBYTE = rotateright(K[ROUND], 4)
-      endfor
-      rotatekey(K, OUTBYTE)
-      OUTBYTE => <OUTSTREAM>
-    endfor
-    
-    func rotatekey(K, B)
-      PREV = K[31]
-      for N in 0..31
-        NEXT = K[N]
-        K[N] = PREV 
-        PREV = NEXT
-        K[N] = KBOX[K[N] xor B]
-      endfor
-    endfunc    
-
-where:
-
-    K[17]: expanded key
-    ROUND: encryption round 1-17
-    INBYTE: one input byte
-    OUTBYTE: encrypted result for output
-    SBOX[256]: pre computed S-Box for encryption
-    rotateleft(B,N): rotate byte B by N bits to the left 
-    rotateright(B,N): rotate byte B by N bits to the right 
-
+FIXME.
 
 ## Analysis so far
 
+These are the results of the previous (128bit) version.
+
 While this stuff only exists for me to play around with
 crypto, I tried to test the cipher a little bit. Here are
 my results using a couple of statistical measurements: