void encrypt(char block, int edflag);
The encrypt() function shall provide access to an implementation-defined encoding algorithm. The key generated by setkey() is used to encrypt the string block with encrypt().
The block argument to encrypt() shall be an array of length 64 bytes containing only the bytes with values of 0 and 1. The array is modified in place to a similar array using the key set by setkey(). If edflag is 0, the argument is encoded. If edflag is 1, the argument may be decoded (see the APPLICATION USAGE section); if the argument is not decoded, errno shall be set to [ENOSYS].
The encrypt() function shall not change the setting of errno if successful. An application wishing to check for error situations should set errno to 0 before calling encrypt(). If errno is non-zero on return, an error has occurred.
The encrypt() function need not be reentrant. A function that is not required to be reentrant is not required to be thread-safe.
The encrypt() function shall not return a value.
The encrypt() function shall fail if:
The functionality is not supported on this implementation.
The following sections are informative.
Historical implementations of the encrypt() function used a rather primitive encoding algorithm.
In some environments, decoding might not be implemented. This is related to some Government restrictions on encryption and decryption routines. Historical practice has been to ship a different version of the encryption library without the decryption feature in the routines supplied. Thus the exported version of encrypt() does encoding but not decoding.
COPYRIGHTPortions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .