This is Crypt::CBC, a Perl-only implementation of the cryptographic cipher block chaining mode (CBC). In combination with a block cipher such as Crypt::DES or Crypt::IDEA, you can encrypt and decrypt messages of arbitrarily long length. The encrypted messages are compatible with the encryption format used by B<SSLeay>. Prerequisites ------------- In addition to this module you will need to install the MD5 module, and one or more of: Crypt::DES, Crypt::DES_EDE3, Crypt::IDEA, Crypt::Blowfish, or Crypt::Rijndael modules. 1. Digest::MD5 Required for key and iteration vector generation. 2. Crypt::DES Required for the DES encryption algorithm. 3. Crypt::DES_EDE3 Required for the triple DES encryption algorithm in Encrypt Decrypt Encrypt mode. Note, this depends on Crypt::DES. 4. Crypt::IDEA Required for the IDEA encryption algorithm. 5. Crypt::Blowfish Required for the Blowfish encryption algorithm. 6. Crypt::Blowfish_PP Required for the Blowfish_PP encryption algorithm. 7. Crypt::Rijndael Required for the Rijndael/AES encryption algorithm. You can find these modules on a CPAN server near you! Unfortunately, Crypt::TripleDES does not work with this module, owing to the fact that it does not follow the same API as the other Crypt::* modules. Please write to TripleDES's author, Vipul Ved Prakash <mail@vipul.net> and ask him to fix this. The Cryptix site also has versions of Crypt::DES and Crypt::IDEA that are slightly different from the CPAN versions. Since these seem to be later versions, I suggest that you download and install the entire Cryptix Perl distribution. In order to get the Crypt:: modules to compile under Perl 5.005 or later, you must add the following line to the DES.xs, IDEA.xs and Blowfish.xs files: #define sv_undef PL_sv_undef For your convenience, a patch file which will bring the Cryptix directory up to date is included in this distribution. It is named cryptix-5.005.patch. Use it like this: % cd Cryptix-1.16 % patch -p1 < ../Crypt-CBC/cryptix-5.005.patch patching file Crypt-Blowfish/Blowfish.xs patching file Crypt-DES/DES.xs patching file Crypt-IDEA/IDEA.xs Then install the Cryptix modules using "perl Makefile.PL; make; make install". Installing Crypt::CBC --------------------- The rest is easy 1. perl Makefile.PL 2. make 3. make test 4. make install Versions 1.22 and greater generate a random initialization vector, rather than generating one based on the key. Not only is this much more secure, but it maintains compatibility with the current version of OpenSSL, which does the same thing as of version 0.9.5. For backwards compatibility, messages encrypted with older versions of Crypt::CBC can be decrypted with the newer version. The reverse is not true -- the beginning messages encrypted by the new version and decrypted by the old may be contaminated with "junk". Lincoln D. Stein lstein@cshl.org