View source for DEA128decrypt and DEA128encrypt (String functions)

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<var>DEA128decrypt</var> and <var>DEA128encrypt</var> are synonyms for the [[String class]] function that applies the DEA (Data Encryption Algorithm) using a 128-bit symmetric key to decrypt or encrypt each 64-bit block of input text. For more details about how the algorithm works, see [https://en.wikipedia.org/wiki/Triple_DES Triple DES].

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 <b><i>always</i></b> hold:
<p class="code">[[Assert statement|assert]] %string:dea128encrypt(%key):dea128decrypt(%key) eq %string
</p>
You can use <var>DEA128decrypt</var> to "document" that you are decrypting, and
use <var>DEA128encrypt</var> to "document" that you are enrypting. You can use <var>DEA128decrypt</var> and <var>DEA128encrypt</var> interchangeably on the rest of this page.

==Syntax==
{{Template:String:DEA128decrypt syntax}}
{{Template:String:DEA128encrypt syntax}}

===Syntax terms===
<table>
<tr><th>%outString</th>
<td>A string variable to receive the encrypted or decrypted method object <var class="term">string</var>. Its length is the same as <var class="term">string</var>.</td></tr>

<tr><th>string</th>
<td>The string to which the method is applied. <var class="term">string</var> must be a multiple of eight bytes in length; its  maximum is 32768 bytes. It may be null.</td></tr>

<tr><th>key</th>
<td>A 16-byte (only) string variable whose value is used to encrypt or decrypt the method object, <var class="term">string</var>.</td></tr>
</table>

==Usage notes==
<ul>
<li>You are <b><i>not</i></b> prevented from creating confusion by encrypting with <var>DEA128decrypt</var> and decrypting with <var>DEA128encrypt</var>. </li>

<li>The <var>DEA128decrypt</var> and <var>DEA128encrypt</var> functions are available as of <var class="product">Model&nbsp;204</var> 7.6. </li>
</ul>

==Examples==
In the following example, the output string from the <var>DEA128encrypt</var> method is converted to hex using the <var>[[StringToHex (String function)|StringToHex]]</var> function to reveal its non-displayable characters, then decrypted to return the original input string:

<p class="code">b                    
%ls is longstring    
%string is longstring
%key is string len 16
%string = 'onetwothreefour0onetwothreefour0'
%key = '1234567816161616'

%ls = %string:dea128encrypt(%key)
[[PrintText statement|printText]] {~} is {%ls:stringTohex}
printText {~} is: {%ls:dea128decrypt(%key)}
end
</p>
The result is:
<p class="output">%ls:stringTohex is: 07A6F72D733C4A333DCB4A8F9661AC8307A6F72D733C4A333DCB4A8F9661AC83
%ls:dea128decrypt(%key) is: onetwothreefour0onetwothreefour0
</p>

==See also==
<ul>
<li><var>[[DEA64decrypt and DEA64encrypt (String functions)]]</var> </li>

<li><var>[[DEA192decrypt and DEA192encrypt (String functions)]]</var> </li>

<li><var>[[DEA64CBCdecrypt and DEA64CBCencrypt (String functions)]]</var> </li>

<li><var>[[DEA128CBCdecrypt and DEA128CBCencrypt (String functions)]]</var> </li>

<li><var>[[DEA192CBCdecrypt and DEA192CBCencrypt (String functions)]]</var> </li>
</ul>

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