Encryption used in GSM communications

[ponnus]

Hai,
I just wanted to know about the encryption standard used in GSM communications.
I'm totally ignorant about encryption standards. Do the standards are different for different frequencies?

and what is 128 bit encryption?

Thank you

 

[FvM]

https://en.wikipedia.org/wiki/A5/1

 

[ponnus]

Hai,
So, is it using 114 bit encryption or 64 bit encryption?

And what about encryption at different frequencies such as for quad band frequencies.

Thank you