MinCrypt
MinCrypt was designed as the minimalistic encryption system to be used within the devices and on the PHP-driven websites. For this purpose there was also a PHP extension written to implement the PHP bindings for the core functionality.
Why is it called MinCrypt?
MinCrypt is the ambiguous project name. Since MinCrypt was written by Michal Novotny in early 2011 the letters Min, or better written as MiN, could mean author initials (Michal Novotny) however the original meaning of the Min letters was to denote the algorithm to be minimalistic and therefore MinCrypt could mean both encryption algorithm by Michal Novotny and minimalistic encryption algorithm.
What is MinCrypt?
As already written above MinCrypt is the minimalistic encryption algorithm implementing several core functions. The encryption itself is symmetric and it's based on the initialization vectors generated from salt and password values and optionally the vector multiplier value.
Initialization vectors are key parts of the encryption system core since once they are generated all the encrypted and decrypted information depends on them and therefore providing the same password and salt values is necessary in order to decrypt the file or data block successfully. The vector multiplier value is useful only for case of bigger data blocks since it's the multiplicator value to expand the initialization vectors table by. Based on vector multiplier's design once the input data block is smaller than data block to be processed the value of this variable will be having no effect.
Using MinCrypt
Once you have the mincrypt installed you can call the binary by running mincrypt from the shell window. You should be also having PHP module installed and loaded in your PHP configuration so you can test it's presence using a standard PHPInfo() output where you could be able to see mincrypt extension information if enabled or you can try to see the mincrypt string in the php -m output (provided the fact you're having access to CGI/CLI-based version of PHP), e.g. using:
$ php -m | grep mincrypt > /dev/null; echo $?
The second part after the semicolon is the next command to be processed and this will redirect the grepped php -m to null device so it will not show the command output. Instead, it will show the error code of the grep command which will be 0 for case the extension is installed properly or number 1 if the extension was not found in your PHP configuration.
If you experience issues that your PHP or Apache dies and your script is running the mincrypt system please check your configuration
Resources
MinCrypt algorithm has been described by it's author in 2010/2011 in the MinCrypt design document (PDF format).