isencrypt(S)

isencrypt -- determine whether a character buffer is encrypted

Synopsis

   cc [flag . . . ] file . . . -lgen [library] . . .
   
   #include <libgen.h>
   

   int isencrypt (const char fbuf, size_t ninbuf);

Description

isencrypt uses heuristics to determine whether a buffer of characters is encrypted. It requires two arguments: a pointer to an array of characters and the number of characters in the buffer.

isencrypt assumes that the file is not encrypted if all the characters in the first block are ASCII characters. If there are non-ASCII characters in the first ninbuf characters, isencrypt assumes that the buffer is encrypted if the setlocale LC_CTYPE category is set to C or ascii.

If the LC_CTYPE category is set to a value other than C or ascii, then isencrypt uses a combination of heuristics to determine if the buffer is encrypted. If ninbuf has at least 64 characters, a chi-square test is used to determine if the bytes in the buffer have a uniform distribution; and isencrypt assumes the buffer is encrypted if it does. If the buffer has less than 64 characters, a check is made for null characters and a terminating new-line to determine whether the buffer is encrypted.

Return values

If the buffer is encrypted, 1 is returned; otherwise zero is returned.

References

setlocale(S)