For encryption/decryption AES in CCM-mode is used. The key is generated via Pbkdf2 from the passphrase.
You may want to visit the excellent SJCL demo to play around with the encryption algorithm.
Default encryption parameters:
Get the python-sjcl source from github:
As a demonstration for both, the API and the cryptography a small backup application is available as part of python-sjcl:
You course you may uses this application to backup the content of your blog.
We do not want to neglect the fact that there are a lot of people who think it's problematic to use cryptography from web based applications.