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20 year old cryptographic puzzle solved by self-taught programmer

World famous architect, Frank Gehry received a time capsule in the month of April in 1999. It had the instructions to be included in his designs for the building which would eventually house the Computer Science and Artificial Intelligence Lab of MIT. It was basically a museum which included the early history of computing. It had items which were contributed by the likes of Tim Berners Lee and Bill Gates.

It was not to be opened for the next 35 years unless someone cracked the cryptographic puzzle which was present in the design. It was made by Ron Rivest, one of the co-inventors of the RSA cryptographic protocol. It was designed in such a way that it would take almost 35 years to compute the answer.

However, on April 15, after almost 20 years the puzzle was announced, it has been solved by Bernard Fabrot, a Belgian programmer. The solution was to be sent to the director for the Laboratory of Computer Science. But Bernard found out that the laboratory did not exist any more. It was merged with CSAIL.


The puzzle was to find a number which was obtained after executing a squaring calculation almost 80 trillion times. After obtaining this number it is to be put in a mathematical operation which uses this and another number which is present in a puzzle. This gives a new number which can be translated to a congratulatory message.

Solving this puzzle needed sequential operations. It means that the calculations had to be approached one by one, as the next step needed the previous result. Thus using powerful machines such as supercomputers was of no use here. Rivest calculated that it would take almost 35 years to come up with the answer to the puzzle.

Bernard Fabrot, an independent developer came to know about the puzzle in 2015. He felt that it could be solved faster using the GNU Multiple Precision Arithmetic Library which is a free software for performing precise arithmetic calculations. Only for solving the puzzle, he dedicated one of his CPU cores to compute the squaring operations and his computer was running 24/7, except when he was holidaying. He solved the puzzle after three and a half years.

Unbeknownst to Fabrot, another group called Cryptophage was also working to solve the puzzle. Led by an ex-Intel engineer, Simon Peffers, this group was working on verifiable delay functions for security operations. With the help of an algorithm designed by Erdinc Ozturk, Sabanci University and a multi-purpose chip they would have solved the puzzle on May 10, but they were beaten by Fabrot just by few days.

About the author: Kalpit Veerwal
Kalpit Veerwal is a second year Computer Science undergraduate at IIT Bombay. He is well known for being the only person to score 360/360 in JEE (Main). He is registered in the Limca Book of Records for the same. A blogger in his free time, he has also secured top ranks in various exams held in India and the world.

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