iOS and AES encryption I have been searching for a diary/journal application for the iPad that will encrypt the contents of the journal. Though there is no shortage of journal and note taking apps I have yet to find one that specifically mentions that the user content is encrypted while on the device. Does iOS provide APIs to allow for AES or similar encryption (Blowfish etc ...)? Is it difficult to encrypt user data within an iOS application? 

Just to clarify ... I am not talking about simple password protection but rather encryption of the user data such that if the iOS device were compromised the user data would be unreadable.
1Password.  Not strictly a note taking application, but it does have secure notes built into it.  You're not going to find markdown support, but you get a place to type text.  Will sync via dropbox with it's desktop version. 

Neither the iOS and OSX/Windows app are free.  (Plus it's a really awesome password vault)