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| <h3 class="section">5.10 Trivial Encryption</h3> |
| |
| <p><a name="index-encryption-580"></a> |
| |
| <p>The <code>memfrob</code> function converts an array of data to something |
| unrecognizable and back again. It is not encryption in its usual sense |
| since it is easy for someone to convert the encrypted data back to clear |
| text. The transformation is analogous to Usenet's “Rot13” encryption |
| method for obscuring offensive jokes from sensitive eyes and such. |
| Unlike Rot13, <code>memfrob</code> works on arbitrary binary data, not just |
| text. |
| <a name="index-Rot13-581"></a> |
| For true encryption, See <a href="Cryptographic-Functions.html#Cryptographic-Functions">Cryptographic Functions</a>. |
| |
| <p>This function is declared in <samp><span class="file">string.h</span></samp>. |
| <a name="index-string_002eh-582"></a> |
| <!-- string.h --> |
| <!-- GNU --> |
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| <div class="defun"> |
| — Function: void * <b>memfrob</b> (<var>void *mem, size_t length</var>)<var><a name="index-memfrob-583"></a></var><br> |
| <blockquote> |
| <p><code>memfrob</code> transforms (frobnicates) each byte of the data structure |
| at <var>mem</var>, which is <var>length</var> bytes long, by bitwise exclusive |
| oring it with binary 00101010. It does the transformation in place and |
| its return value is always <var>mem</var>. |
| |
| <p>Note that <code>memfrob</code> a second time on the same data structure |
| returns it to its original state. |
| |
| <p>This is a good function for hiding information from someone who doesn't |
| want to see it or doesn't want to see it very much. To really prevent |
| people from retrieving the information, use stronger encryption such as |
| that described in See <a href="Cryptographic-Functions.html#Cryptographic-Functions">Cryptographic Functions</a>. |
| |
| <p><strong>Portability Note:</strong> This function is unique to the GNU C library. |
| |
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