DEA64decrypt and DEA64encrypt (String functions)

From m204wiki
Jump to navigation Jump to search

DEA64 encryption or decryption (String class)

[Introduced in Model 204 7.6]

DEA64decrypt and DEA64encrypt are synonyms for the String class function that applies the DEA (Data Encryption Algorithm) using a 64-bit symmetric key to decrypt or encrypt each 64-bit block of input text. For more details about how the algorithm works, see Data Encryption Standard.

The length of the returned string is the same as that of the object string.

DEA is a two-way cipher, so encrypting a string with a key and then decrypting the result of that encryption with the same key produces the original string. That is, the following assertion should always hold:

assert %string:dea64encrypt(%key):dea64decrypt(%key) eq %string

You can use DEA64decrypt to "document" that you are decrypting, and use DEA64encrypt to "document" that you are encrypting. You can use DEA64decrypt and DEA64encrypt interchangeably on the rest of this page.


%outString = string:DEA64decrypt( key) Throws UnsupportedCrypto, InvalidCryptoKey, InvalidCryptoData

%outString = string:DEA64encrypt( key) Throws UnsupportedCrypto, InvalidCryptoKey, InvalidCryptoData

Syntax terms

%outString A string variable to receive the encrypted or decrypted method object string. Its length is the same as string.
string The string to which the method is applied. string must be a multiple of eight bytes in length; its maximum is 32768 bytes. It may be null.
key An 8-byte (only) string variable whose value is used to encrypt or decrypt the method object, string.

Usage notes

  • You are not prevented from creating confusion by encrypting with DEA64decrypt and decrypting with DEA64encrypt.
  • The DEA64decrypt and DEA64encrypt functions are available as of Model 204 7.6.


In the following example, the output string from the DEA64encrypt method is converted to hex using the StringToHex function to reveal its non-displayable characters, then decrypted to return the original input string:

b %ls is longstring %string is longstring %key is string len 8 %string = 'onetwothreefour0onetwothreefour0' %key = '12345678' %ls = %string:dea64encrypt(%key) printText {~} is {%ls:stringTohex} printText {~} is: {%ls:dea64decrypt(%key)} end

The result is:

%ls:stringTohex is: A54138C10468C061567574F88567E221A54138C10468C061567574F88567E221 %ls:dea64decrypt(%key) is: onetwothreefour0onetwothreefour0

See also