Numeric Base Conversion

string function Base2Base(InputNumber as string, InputBase as integer, OutputBase as integer)

   Dim J, K, DecimalValue, X, MaxBase, InputNumberLength as integer
   Dim NumericBaseData, OutputValue as string

   NumericBaseData = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"

   MaxBase = Length(NumericBaseData)

   if (InputBase > MaxBase) OR (OutputBase > MaxBase) then
      Base2Base = "N/A"
      return
   end if

*/ Convert InputNumber to Base 10 /*

   InputNumberLength = Length(InputNumber)
   DecimalValue = 0

   for J = 1 to InputNumberLength
      for K = 1 to InputBase
         if mid(InputNumber, J, 1) == mid(NumericBaseData, K, 1) then
            DecimalValue = DecimalValue+int((K-1)*(InputBase^(InputNumberLength-J))+.5)
         end if
      next K
   next J

*/ Convert the Base 10 value (DecimalValue) to the desired output base /*

   OutputValue = ""

   while DecimalValue > 0
      X = int(((DecimalValue/OutputBase)-int(DecimalValue/OutputBase))*OutputBase+1.5)
      OutputValue = mid(NumericBaseData, X, 1)+OutputValue
      DecimalValue = int(DecimalValue/OutputBase)
   loop

   Base2Base = OutputValue

   return
end

There are a number of enhancements that can be made to this function to make it more suitable for specific applications.  For instance, if you are only converting between Binary, Octal, and Decimal, you can reduce the size of the NumericBaseData string to 0-9, or even use a different function that doesn't use strings at all. If the maximum base you're dealing with is Base 16 (Hexadecimal) reduce NumericBaseData to the digits 0-9 and the letters A-F.

By adding a space character " " to NumericBaseData, you can use this algorithm for encrypting text with capital letters and numbers.  You could make the encryption more secure by shuffling the order of the letters and numbers.  By increasing NumericBaseData to include lower case letters and punctuation, as well as digits and capital letters, you could make the encryption even more secure.  The senders and receivers of the messages would have to have identical copies of NumericBaseData then they only need to send the input and output base numbers with the encrypted messages in order to decipher them.


If you want to use this algorithm for encryption but you don't want it to look like an encrypted message you could add the following modifications:

Replace NumericBaseData with several string arrays.  Each array would include whole words that are commonly used in speech as well as words used specifically for the task at hand and as many uncommon words that are unrelated to the task at hand as you can.  There would be separate arrays for each part of speech, ie. a noun array, a verb array, a preposition array, an adjective array, an adverb array, etc.  Each array would have to have the same number of words.  In order to keep from decrypting the message incorrectly, there could be no duplication of words between arrays.  For instance, the word 'fast' can be used as a noun, verb, adjective, or adverb depending on the context of the sentence.  In cases like this, put the word in the array where it is used most often, or don't use it at all.  When encrypting the original message, each word would be replaced with a different word of the same part of speech.  A casual observer of the encrypted message would read normal language but not be able to decipher the message, or the message would appear to give false information about the subject matter.


While I have not yet implemented such code, bookmark this page and check back occasionally for updates on ways to encrypt text messages with other types of text messages.

Maurice Kherlakian has been kind enough to translate the the code listed above to PHP. Maurice's code follows and includes a test at the end to demonstrate the speed of the routine. In testing, Maurice was able to perform about 13,000 conversions per second, but it was not stated what hardware was being used for the speed test.

<?php

define('BASE_CONV',
'0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz');

function base2Base($inputNumber, $inputBase, $outputBase) {
	$maxBase = strlen(BASE_CONV);
	
	if($inputBase > $maxBase || $outputBase > $maxBase) {
		return 'N/A';
	}
	
	/* Convert input number to base 10 */
	$inputNumberLength = strlen($inputNumber);
	$decimalValue = 0;
	
	for($j = 0; $j < $inputNumberLength; $j++) {
		for($k = 0; $k < $inputBase; $k++ ) {
			if(substr($inputNumber, $j, 1) == substr(BASE_CONV, $k, 1)) {
				$decimalValue = $decimalValue + (int)(($k)*bcpow($inputBase, $inputNumberLength - ($j+1)) + 0.5);
				break;
			}
		}
	}
	//for debugging. Comment out.
	echo 'in decimal value: ' . $decimalValue . '<br />';
	
	$outputValue = "";
	
	
	do {
		$x=(int)((($decimalValue/$outputBase) - (int)($decimalValue/$outputBase))*$outputBase + 1.5);
		$outputValue = substr(BASE_CONV, $x - 1, 1) . $outputValue;
		$decimalValue = (int)($decimalValue/$outputBase);
	} while($decimalValue > 0); 

	//for debugging. Comment out.	
	echo "out base " . $outputBase . " value: " . $outputValue . '<br />';
	return $outputValue;
}

//Testing.
$start = time();
echo time();

for($i=0; $i < 2048; $i++) {
	base2Base($i, 10, 62);	
}

$end = time() - $start;
echo time();

?>