Intercept and Listen calls on GSM mobile :)

INTERCEPT AND LISTEN CALLS ON GSM MOBILE 

1) Decrytping GSM phone called A5/1 is a flow encryption used to provide over the air (OTA)  communication privacy in the standard GSM cell phone. It was initially kept secret, but was made public through leaks and reverse engineering.

2) A number of serious deficiencies in the encryption system have been identified . The first is an active attack.

3) GSM phones can be convinced to use the much weaker A5/2 briefly encrypted . A5/2 can be easily broken , and the phone uses the same key as the strongest A5/1 algorithm. A second attack in A5/1 is outlined , an encrypted text , only time memory attack handicap that requires a lot of precalculation .

3) GSM Decryption

>recording GSM data can be recorded out of the air using, for example, a programmable radio such as the USRP.

4) When GSM uses A5/1 encryption, the secret key can be extracted from registered traffic.

5)  Given two encrypted known clear text messages, the Kraken utility example  that runs on a PC finds the secret key with a probability of about 90% in a matter of seconds in a set of rainbow tables

6) A set known current table took 2 months to calculate and contains 40 tables for a total of 2 TB.

Defenses:-
1) Short term protocol patches already exist which makes cracking much more difficult for not revealing plain text known unnecessarily (). These patches should be deployed with high priority.

2) In the long term, GSM (2G) does not provide sufficient security and more powerful alternatives such as UMTS (3G) and LTE (4G) should be preferred.

Instruments For decrypting :-
The following tools are used to analyze voice calls:

• GNU Radio
• Airprobe
• Kraken

GNU Radio is included in recent Linux distributions.Data logging requires a programmable radio receiver such as the USRP.







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