-----BEGIN PGP SIGNED MESSAGE----- Here is the RC4 cipher for the HP-48 calculator. It complements the DES implementation by William E. Sommerfeld. RC4 has a higher throughput than DES, but its key setup is slower. The key may be up to 256 characters (2048 bits) -- the maximum supported by the RC4 algorithm. Here are sample timings for a HP-48GX. The SX will be correspondingly slower. Key Setup (200 bits) 25.18 sec RC4 throughput 5.06 cps String to Array 61.83 cps Array to String 56.12 cps The HP-48 comes with a 2400 baud IR link and a 1200/2400/9600 baud RS232 port. The 48S, 48SX and 48G have 32Kb of RAM, almost none of which is used by the operating system. The 48GX has 128Kb of RAM. With an entry price of ~100$ US, I feel that the HP-48 series would be a good choice for a smart token. Possible uses are as digital cash wallets and authentication tokens, not the mention simple encrypted dumb terminals. Installation: If you have a serial cable, download the code below to your HP and call it 'RC4'. This will create a directory called 'RC4' with four programs in it. If you don't have a cable you can type the whole thing in; it's not too large. Store it as 'RC4' and again it will create a directory. Remember not to type the "%%HP: T(3)A(D)F(.);" -- it's only needed for a serial download. Instructions: These instructions assume that you are familiar with stream-ciphers in general. If you are not, you might want to get _Applied Cryptography_ by Bruce Schneier from your library or book store. Bit streams are represented as one dimensional arrays of real numbers between 0 and 255. Yes, that's right, this cipher uses floating-point! In User-RPL it's the fastest way. To convert between strings and arrays use the commands S2A and A2S. S2A "String" -> [Array] A2S [Array] -> "String" To setup a key, use the SK command. It takes a bitstream representing the keytext and returns the key context. They keytext can be up to 256 bytes long. Additional bytes will not be used. The key context is another bitstream with 256 values in it. Because of time/memory tradeoffs, a key context takes 2082 bytes of RAM to store. If memory is tight, use A2S to compress the key context to a string. SK [Key text] -> [Key context] To encrypt something use the RC4 command. The first argument is the key context, the second is the plaintext or ciphertext, both in bitstream form. It returns the updated key context and the ciphertext or plaintext. RC4 [Key context], [Plaintext] -> [New key context], [Ciphertext] or RC4 [Key context], [Ciphertext] -> [New key context], [Plaintext] Enjoy The Cunning Artificers - -- CUT HERE -- %%HP: T(3)A(D)F(.); DIR SK \<< DTAG OBJ\-> OBJ\-> DROP 0 255 FOR N N NEXT 259 258 PICK + 0 259 4 FOR N OVER PICK N PICK + + 256 MOD DUP 255 - NEG N 4 - DUP2 IF \=/ THEN DUP2 IF > THEN SWAP END DUP2 6 + ROLL SWAP 6 + ROLL SWAP 4 ROLL 5 + ROLLD SWAP 3 + ROLLD ELSE DROP2 END SWAP 1 - DUP IF 260 < THEN DROP 258 PICK 259 + END SWAP -1 STEP DROP2 0 0 258 \->ARRY OVER 2 + ROLLD DROPN "Key" \->TAG \>> RC4 \<< DTAG DUP SIZE OBJ\-> DROP 3 PICK 258 GET 4 PICK 257 GET 1 + 1 4 ROLL FOR N 256 MOD 1 + DUP 5 PICK SWAP GET 3 ROLL + 256 MOD 1 + DUP 5 ROLL SWAP 4 PICK CSWP DUP DUP 5 PICK GET OVER 5 PICK GET + 256 MOD 1 + GET 5 ROLL DUP N GET R\->B 3 ROLL R\->B XOR B\->R N SWAP PUT 4 ROLL 4 ROLL 1 - SWAP NEXT 4 ROLL 257 3 ROLL 1 - PUT 258 3 ROLL PUT "Updated key" \->TAG SWAP "Result" \->TAG \>> S2A \<< DUP SIZE \<< \-> LEN \<< 1 LEN START DUP NUM SWAP TAIL NEXT DROP LEN \>> \>> EVAL 1 \->LIST \->ARRY \>> A2S \<< DTAG OBJ\-> OBJ\-> DROP "" SWAP 1 SWAP START SWAP CHR SWAP + NEXT \>> END - -- CUT HERE -- - -----BEGIN PGP PUBLIC KEY BLOCK----- Version: 2.6.2 mQCNAzEAEf4AAAEEAMONoLHj5CwKvaM6ch9GOcUjgoVS5sjXa4TzD2ohhtHFYR9l QzNj0vNASBQKE/Mk9Flqg+dtitS7S7B0qZQ+mQmMT73yniun596jt1NCJ5sLBKrM jDvYK3wGbycVX43RBiR3iwJZGq5blfWqNRE7kFdTxgu+bCdtLOFNVew9oBf9AAUR tBZUaGUgQ3VubmluZyBBcnRpZmljZXJz =pf3Y - -----END PGP PUBLIC KEY BLOCK----- -----BEGIN PGP SIGNATURE----- Version: 2.6.2 iQCVAwUBMQRCWuFNVew9oBf9AQEPJgP/QzwxGIWU0sf+a8Vzj2tXtMqRhRQjG4Qp Pcrwr76WhM/2KnHGNAdC3lKwyEK17cu32zbmPePhOvtdUNyV3L1KZlBioURK5Kxu ZspnOLCmlKo8lbOa5mJl2bmV55W49B96ua+yxst1XaOzhfYDN/KjZsztGRnEbQx9 VovMpLXooLo= =4pzv -----END PGP SIGNATURE-----