From MozillaZine Knowledge Base
(Redirected from 128-bit Encryption)
Mozilla Suite, Firefox, and Thunderbird support up to 256-bit encryption (although it's not commonly used) and is suitable for secure transfers on the Internet. You can use Mozilla Suite, Firefox, and Thunderbird with your bank or any other financial instution that requires strong encryption to protect your personal data. You can also set Mozilla Suite and Firefox to give you an alert when you access a secure page and when you leave a secure page.
Some websites incorrectly detect encryption capabilities and report that Mozilla Suite and Firefox do not have 128-bit encryption. You may be able to get around this problem by changing the browser's user agent string to that of Internet Explorer.