APCO25 Encryption
DISCLAIMER
The information contained herein are for educational purposes only. Do not attempt to circumvent or crack DES. This is a criminal offence. Do not email or message me for information on how to encrypt or crack DES. You will simply get no reply.
I am no telecommunication engineer and I may have made some technical errors somewhere within this document. If you do find any please be nice enough and point them out!
First there is digital - APCO25
Encryption has been made possible by the introduction of APCO25 Digital Radio networks developed by the Association of Public Safety Communications Officials International (APCO). The numerals 25 stand for Project number 25. P25 is not neccessarily a single standard but a set of standards which may be used by the Users of the network - In this case the government or users within the Government Radio Network.
The Australian Government has already successfully integrated digital APCO25 standards across major metropolitan areas such as Melbourne - with encryption (or ENC) already in place or Sydney and surrounding areas where APCO25 Digital is already implemented but not yet encrypted.
P25 is extremely versatile and may be used for Voice, Data or both at the same time, both in the clear of in encrypted state. Trunking networks such the the government radio network, can also make use of P25. Furthermore it is fully backwards compatible - ie. it is capable of transmitting on 25KHz channels in analog mode.
Introduction to Encryption
The technical details of encryption are very complicated and may be too much to explain if we went into detail. So instead we stick to the simple basics.
The encryption standard that is believed to be used by the Australian Government is called Data Encryption Standard (also DES) or Advanced Encryption Standard (AES) - I will only cover DES here as I belive APCO25 will make use of DES only.
The process involved in enciphering (encrypting) and de-decyphering (decrypting) consist of complicated mathematical algorithms.
When data is encrypted, it is converted to an unreadable form which is referred to as a cipher. When a cipher is decrypted containing data is reverted to its original source - so in this case clear voice or data.
The earlier mentioned algorithm is specified by a binary number called a key. This is the key to decypher and encypher data or voice.
In the process of encyphering (encrypting), 16 rounds are done to scramble the key and the containing data. This ensures a high degree of security.
Now it becomes technical.
This key consists of 64 digits in binary form 0s and 1s. 56 of this binary bits are randomly generated by this algorithm and used by it immediatley. Then we have 8 bits remaining.
For anyone that has some computer programming knowledge would be used to the term parity. For those who dont, parity is used by both hardware and software for error detection. I will not go into more detail as I dont want to confuse you more than you probably already are.
Only radio users that have direct access to this unique key will be able to quickly and effiecently decypher any incoming radio transmissions.
In most cases though, the user will actually never see the 64 digit key as it is broadcast to authorised radio systems automatically.
To add to the security mentioned above, the key is usually changed every 7 - 14 days depending on the application of the system.
So...how secure is it?
The simple answer would be; extremely
But. There has been a lot done to test DES over the 25 odd years. Machines have been constructed for under $500,000 US that would decypher the key under seven days.
This image depicts the COPACOBANA machine, built for US$10,000 by the Universities of Bochum and Kiel. This machine was able to crack DES in a matter of days using relatively low cost components.
For normal household standards, the average Mac or PC will not be capable of succesfully cracking the DES encryption.
As said in my disclaimer, attempting to crack DES will end you up in court and you may end up in jail.
How do I know if my area uses encryption?
Why not drop into our forums and ask the question there?
What does all this mean for scanning enthusiasts?
With the introduction of this technology, listening to emergency services will become increasingly difficult. Even with digital scanners available today, listening will become impossible and illegal (if you happen to come across the key).
So the bottom line is that we will need to shift our interests to other areas of scanning that are still open to the public ear - such as Air Traffic, Private sector companies and the government radio network.
