The PS3's version of the Cell will not come close to 1.8 Tflops ( btw that was the numbers for the GPU on the PS3 , which no one believed)
Fact is the Cell will not come close to 256 gflops. it would be much closer to 20 gflops. The Cell is limited by the platform, which is severely hampered by the amount of ram.
Consider this "The amount of time required to break a 128-bit key is also daunting. Each of the 2^128 (340,282,366,920,938,463,463,374,607,431,768,211,456) possibilities must be checked. A device that could check a billion billion keys (1018) per second would still require about 1013 years to exhaust the key space. This is a thousand times longer than the age of the universe, which is about 13,000,000,000 (1.3×1010) years" Wiki.
So good luck, but maybe we can focus resources in to something practical, important, and ACHIEVABLE.