FileMaker Pro Custom Functions

/** * ===================================== * ChaosDecrypt ( cipherText ; key ) * * WARNING: * Different versions of the ChaosEncrypt and ChaosDecrypt functions are * unlikely to be compatible. * * PURPOSE: * Uses chaotic permutations of the key to create an decrypted version of * cipherText that was created by the ChaosEncrypt() function. This function * uses a psuedo-chaotic stream cipher algorithm adapted to the constraints of * FileMaker custom functions. * * PARAMETERS: * cipherText: The text string to decrypt * key: The key to used to encrypt cipherText * * RETURNS: * A decrypted version of cipherText. * * NOTES: * This function has not been subjected to rigorous cryptanalysis, and the * author does not warranty the security of encrypted text. * * This is a recursive custom function, and hence is limited in the maximum * combined length of text and key that it can decrypt. * * HISTORY: * MODIFIED on 2011-01-23 by Jeremy Bante to account for composite * characters. * MODIFIED on 2011-01-14 by Jeremy Bante to use a different map and * systematically perturbed orbits. * MODIFIED on 2011-01-09 by Jeremy Bante to use a different chaotic * map that results in greater diffusion and faster calculation. * MODIFIED on 2011-01-05 by Jeremy Bante to use a different chaotic * map when transforming the key. * CREATED on 2011-01-04 by Jeremy Bante of The Support Group. * * REFERENCES: * ChaosDecrypt function: http://www.briandunning.com/cf/1259 * ChaosEncrypt function: http://www.briandunning.com/cf/1258 * ChaosHash function: http://www.briandunning.com/cf/1261 * ===================================== */ Case ( /*First call to function; initialize variables*/ not $~step; Let ( [ $~keyLength = Length ( key ); $~priorByte = 32749; //greatest prime < 2^15 $~step = 1 ]; ChaosDecrypt ( cipherText ; key ) ); /*Step 1, convert key to numbers and scramble first round*/ $~step = 1; Let ( [ //extract next byte from key, accounting for composite characters ~keyByte = Code ( Left ( key ; 1 ) ); ~extraByte = Left ( ~keyByte ; Length ( ~keyByte ) - 5 ); ~keyByte = Mod ( Right ( ~keyByte ; 5 ) + $~priorByte ; 65535 ); //iterate ~keyByte through the map 8x, perturb 4th orbits ~keyByte = Mod ( 4099 * ( 65535 - ~keyByte ) ; 65535 ); ~keyByte = Mod ( 4099 * ( 65535 - ~keyByte ) ; 65535 ); ~keyByte = Mod ( 4099 * ( 65535 - ~keyByte ) ; 65535 ); ~keyByte = Mod ( 4099 * ( 65535 - ~keyByte ) + 1; 65535 ); ~keyByte = Mod ( 4099 * ( 65535 - ~keyByte ) ; 65535 ); ~keyByte = Mod ( 4099 * ( 65535 - ~keyByte ) ; 65535 ); ~keyByte = Mod ( 4099 * ( 65535 - ~keyByte ) ; 65535 ); ~keyByte = Mod ( 4099 * ( 65535 - ~keyByte ) + 1 ; 65535 ) + 1; //add new value to list $~key = List ( ~keyByte ; $~key ); $~priorByte = ~keyByte; //continue until whole key is processed ~keyLength = Length ( key ); $~step = If ( ~keyLength > 1 ; $~step ; /*else*/ $~step + 1 ) ]; ChaosDecrypt ( cipherText; Char ( ~extraByte ) & Right ( key ; ~keyLength - 1 ) ) ); /*Step 2, apply key to text*/ $~step = 2; Let ( [ ~keyByte = Mod ( GetValue ( $~key ; 1 ) + $~priorByte ; 65535 ); //iterate ~keyByte through the map 8x, perturb 4th orbits ~keyByte = Mod ( 4099 * ( 65535 - ~keyByte ) ; 65535 ); ~keyByte = Mod ( 4099 * ( 65535 - ~keyByte ) ; 65535 ); ~keyByte = Mod ( 4099 * ( 65535 - ~keyByte ) ; 65535 ); ~keyByte = Mod ( 4099 * ( 65535 - ~keyByte ) + 1; 65535 ); ~keyByte = Mod ( 4099 * ( 65535 - ~keyByte ) ; 65535 ); ~keyByte = Mod ( 4099 * ( 65535 - ~keyByte ) ; 65535 ); ~keyByte = Mod ( 4099 * ( 65535 - ~keyByte ) ; 65535 ); ~keyByte = Mod ( 4099 * ( 65535 - ~keyByte ) + 1 ; 65535 ) + 1; //extract next byte from cipherText, accounting for composite characters ~cipherByte = Code ( Left ( cipherText ; 1 ) ); ~extraByte = Left ( ~cipherByte ; Length ( ~cipherByte ) - 5 ); ~cipherByte = Right ( ~cipherByte ; 5 ); //apply key to text //additive complement under 2^16 is analogous to XOR in binary encryption ~plainByte = 65535 - Mod ( ~cipherByte + ~keyByte ; 65535 ); $~plainText = $~plainText & Char ( ~plainByte ); //rotate the key $~priorByte = ~cipherByte; $~key = Substitute ( List ( RightValues ( $~key ; $~keyLength - 1 ) ; ~keyByte ); "¶¶"; "¶" ); //continue until whole text is encrypted ~textLength = Length ( cipherText ); $~step = If ( ~textLength > 1 ; $~step ; /*else*/ $~step + 1 ) ]; ChaosDecrypt ( Char ( ~extraByte ) & Right ( cipherText ; ~textLength - 1 ); "" ) ); /*Step 3, clean-up and return result*/ $~step = 3; Let ( [ ~plainText = $~plainText; //purge variables $~key = ""; $~keyLength = ""; $~plainText = ""; $~priorByte = ""; $~step = "" ]; ~plainText ) )
 Then copy & paste into FileMaker Advanced's Edit Custom Function window.