# 128 bit encryption - Factorization

Discussion in 'Mathematics and Physics' started by neptune, Apr 23, 2014.

1. ### neptuneMember

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Hello,
I am back after long time

Everyone knows that factorizing 2^128 bit long number takes long time for computer, especially when it is a product of two equally long prime numbers.
My question is - why do they not maintain a list of prime numbers and their factors in a look up table, one wouldn't need to check what's the factor of the code is by normal division, number after number.
look up table could be like this-

11*11 = 121
11*13 = 143
11*17 = 187
...
...
13*13 = 169
13*17 = 221
...
...

2. ### nsaspookWell-Known Member

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Applied Cryptography by Bruce Schneier
((2^511) * 1) / (512 log(2)) = 4.35 × 10e151

I haven't worked out the math for size but the 128 bit database would also be pretty big.

Last edited: Apr 23, 2014
3. ### neptuneMember

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Holy Sh.it !

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5. ### MrAlWell-Known MemberMost Helpful Member

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Hi,

Some enumerations of things dont seem that they could be that large, but then when we do the math we find out just how large some things can really be. Look at the number of possible legal chess positions in a normal chess game (the chess board only has 64 squares, and 16 pieces and 16 pawns at the start). That number is bigger than the number of atoms in the universe !