Contents
Why AES-GCM is better?
GCM provides authentication, removing the need for an HMAC SHA hashing function. It is also slightly faster than CBC because it uses hardware acceleration (by threading to multiple processor cores). AES-128 provides more than enough security margin for the foreseeable future.
How strong is AES-GCM?
This beast is capable of a peak speed of 93.02 petaflops. This means that the most powerful computer in the world would still take some 885 quadrillion years to brute force a 128-bit AES key. The number of operations required to brute force a 256-bit cipher is 3.31 x 10^56.
Why does OpenSSL not include AES-256-GCM?
If it is unavailable on your platform (OpenSSL added GCM support in 1.0.1, I believe), I have also implemented an CBC-HMAC and CTR-HMAC. If you’ve installed a later version of OpenSSL, you need to ensure the Ruby binary you’re using is linked against that version. It is probably not. Details for doing this are rbenv- and rvm-specific.
Is the GCM tag stored in OpenSSL ENC?
The enc program does not support authenticated encryption modes like CCM and GCM. The utility does not store or retrieve the authentication tag. This answers your question, I suppose — depending on which version of OpenSSL you are using. The GCM tag is not stored in the output file when using the openssl enc app.
Are there any authenticated encryption modes in OpenSSL?
I was accidentally using LibreSSL openssl. Reading a current version of the OpenSSL documentation for the enc tool, it contains the following sentence The enc program does not support authenticated encryption modes like CCM and GCM. The utility does not store or retrieve the authentication tag.
Is there a command line tool for AES GCM?
When it comes to “commonly available command line tools”, AES GCM is not available. The closest thing is probably AESCRYPT, which has the advantage of a documented file format and implementations in a number of languages.