Convert::PEM::CBC(3) User Contributed Perl Documentation Convert::PEM::CBC(3)NAMEConvert::PEM::CBC - Cipher Block Chaining Mode implementation
SYNOPSIS
use Convert::PEM::CBC;
my $cbc = Convert::PEM::CBC->new(
Cipher => 'Crypt::DES_EDE3',
Passphrase => 'foo'
);
my $plaintext = 'foo bar baz';
$cbc->encrypt($plaintext);
DESCRIPTIONConvert::PEM::CBC implements the CBC (Cipher Block Chaining) mode for
encryption/decryption ciphers; the CBC is designed for compatability
with OpenSSL and may not be compatible with other implementations (such
as SSH).
USAGE
$cbc = Convert::PEM::CBC->new(%args)
Creates a new Convert::PEM::CBC object and initializes it. Returns the
new object.
%args can contain:
· Cipher
Either the name of an encryption cipher class (eg. Crypt::DES), or
an object already blessed into such a class. The class must support
the keysize, blocksize, encrypt, and decrypt methods. If the value
is a blessed object, it is assumed that the object has already been
initialized with a key.
This argument is mandatory.
· Passphrase
A passphrase to encrypt/decrypt the content. This is different in
implementation from a key (Key), because it is assumed that a
passphrase comes directly from a user, and must be munged into the
correct form for a key. This "munging" is done by repeatedly
computing an MD5 hash of the passphrase, the IV, and the existing
hash, until the generated key is longer than the keysize for the
cipher (Cipher).
Because of this "munging", this argument can be any length (even an
empty string).
If you give the Cipher argument an object, this argument is
ignored. If the Cipher argument is a cipher class, either this
argument or Key must be provided.
· Key
A raw key, to be passed directly to the new cipher object. Because
this is passed directly to the cipher itself, the length of the key
must be equal to or greater than the keysize for the Cipher.
As with the Passphrase argument, if you give the Cipher argument an
already-constructed cipher object, this argument is ignored. If the
Cipher argument is a cipher class, either this argument or
Passphrase must be provided.
· IV
The initialization vector for CBC mode.
This argument is optional; if not provided, a random IV will be
generated. Obviously, if you're decrypting data, you should provide
this argument, because your IV should match the IV used to encrypt
the data.
$cbc->encrypt($plaintext)
Encrypts the plaintext $plaintext using the underlying cipher
implementation in CBC mode, and returns the ciphertext.
If any errors occur, returns undef, and you should check the errstr
method to find out what went wrong.
$cbc->decrypt($ciphertext)
Decrypts the ciphertext $ciphertext using the underlying cipher
implementation in CBC mode, and returns the plaintext.
If any errors occur, returns undef, and you should check the errstr
method to find out what went wrong.
$cbc->iv
Returns the current initialization vector. One use for this might be to
grab the initial value of the IV if it's created randomly (ie. you
haven't provided an IV argument to new):
my $cbc = Convert::PEM::CBC->new( Cipher => $cipher );
my $iv = $cbc->iv; ## Generated randomly in 'new'.
Convert::PEM uses this to write the IV to the PEM file when encrypting,
so that it can be known when trying to decrypt the file.
$cbc->errstr
Returns the value of the last error that occurred. This should only be
considered meaningful when you've received undef from one of the
functions above; in all other cases its relevance is undefined.
AUTHOR & COPYRIGHTS
Please see the Convert::PEM manpage for author, copyright, and license
information.
perl v5.14.1 2010-12-07 Convert::PEM::CBC(3)