An IT worker from British Airways jailed for 30 years for terrorism offences used encryption techniques that pre-date the birth of Jesus.

Rajib Karim, 31, from Newcastle, was found guilty of attempting to use his job at BA to plot a terrorist attack at the behest of Yemen-based radical cleric Anwar al-Awlaki, a leader of al-Qaeda in the Arabian Peninsular.

Sentencing him at Woolwich Crown Court last week, Justice Calvert-Smith described Karim as a "committed jihadist" who responded "enthusiastically" towards plans to smuggle a bomb onto a plane or damage BA's IT systems.

Justice Calvert-Smith praised police for being able to decipher incriminating documents under "five or more layers of protection", the Daily Telegraph reports.

However, claims by the prosecution that the coding and encryption systems were the most sophisticated ever seen in use were overstated – by more than 2,000 years.

Woolwich Crown Court was told that Bangladeshi Islamic activists who were in touch with Karim had rejected the use of common modern systems such as PGP or TrueCrypt in favour of a system which used Excel transposition tables, which they had invented themselves.

But the underlying code system they used predated Excel by two millennia. The single-letter substitution cipher they used was invented by the ancient Greeks and had been used and described by Julius Caesar in 55BC.

Karim, an IT specialist, had used PGP, but for storage only.

Despite urging by the Yemen-based al Qaida leader Anwar Al Anlaki, Karim also rejected the use of a sophisticated code program called "Mujhaddin Secrets", which implements all the AES candidate cyphers, "because 'kaffirs', or non-believers, know about it so it must be less secure".

The majority of the communications that formed the basis of the case against Karim, which claimed to warn of a possible terrorist plot in the making, were exchanged using the Excel spreadsheet technique, according to the prosecution.

Writer Duncan Campbell, who acted as an expert witness for the defence during the trial, said: "Tough communication interception laws [RIPA] were passed in the UK 10 years ago on the basis that they were needed to fight terrorism. Ludicrous articles were published then about the alleged sophistication of their methods.

"The case just dealt with shows where we have got to in the real world. The level of cryptography they used was not even up to the standards of cryptology and cryptography in the Middle Ages, although they made it look pretty using Excel." ®

Campbell will be writing for the Register on insights into terrorists' use of cryptography soon.