LastPass has created this page to help verify the encryption methods used by LastPass.
To use this tool you must enter your LastPass Username and LastPass Master Password. You can then encrypt or decrypt any data that was encrypted by LastPass. All encrypted data is base64'ed.

This page has no network connectivity. It is 100% local JavaScript. You can utilize TamperData in Firefox to collect your data to test against these results. This same method is applied to allow login via a web page without ever sending your master password / key to LastPass.

LastPass Email
LastPass Password
Number of PBKDF2 Iterations