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Name

isencrypt - determine whether a buffer of characters is encrypted

Synopsis

cc [ flag ... ] file ... -lgen [ library ... ]

#include <libgen.h>

int isencrypt(const char *fbuf, size_t ninbuf);

MT-Level

MT-Safe

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.

See Also

setlocale(3C)

Notes

When compiling multi-thread applications, the _REENTRANT flag must be defined on the compile line. This flag should only be used in multi-thread applications.

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