Can not login. Error writing request: The authentication or decryption has failed

This problem is not directly related to JiraTouch. It means that you have a problem with your Jira installation specifically with your root certificates.

You can check out the following links for the causes and possible solutions.

http://forums.developer.mindtouch.com/showthread.php?t=2790
http://www.mono-project.com/FAQ:_Security