# CIS Documentation
# M. Divjak / 2011-07-01


CIS DOCUMENTATION

Encrypted archives - Ciphering programs - CipherSaber and RC4 -
Compile and install - Usage - Caveats


Encrypted archives

    One of the best places for data archives are magnetic disks on
    networked servers. However, any data placed on those servers
    becomes easily accessible to every user with a proper account.
    Therefore, it needs to be encrypted before uploading.


Ciphering programs

    Many encrypting / decrypting programs exist, both free and
    commercial. However it is best to write one's own program based
    on some simple yet strong ciphering algorithm. Such a program
    is fully transparent and does not contain any malicious code.
    It can be re-written in another language or re-compiled on
    another platform. If the ciphering algorithm is reasonably
    strong, the encrypted data becomes safe from all but most
    resolute intruders, and that is what most of us are looking
    for.


CipherSaber and RC4

    CIS is a program of this kind and uses the same secret key to
    encrypt and decrypt a computer file. It is based on A. G.
    Reinhold's CipherSaber protocol, which itself is based on R.
    Rivest's RC4 ciphering algorithm. The algorithm is easy to
    program and is strong enough to be used by today's web browsers
    in SSL protocols for securing credit card forms.


Compile and install

    Compile the source file cis.c:

        gcc -o cis cis.c

    Copy the binary file cis to a suitable directory, for example
    to /usr/local/bin, and make it executable.


Usage

    To encode a file:

        cis -e SECRETKEY <infile> <outfile>

    To decode a ciphered file:

        cis -d SECRETKEY <infile> <outfile>

    The SECRETKEY is a suitable password (eg. MySecretKey) or a
    quote-delimited passphrase (eg. "My Secret Key").


Caveats

    The secret key length shall exceed 128 bits, i.e. 16
    characters.

# end

