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snucrypto / HEAAN

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Inverse of ciphertext #2

Closed Subanggu closed 6 years ago

Subanggu commented 6 years ago

Hi. I tested the function 'testInverseBatch' in TestScheme. This function is very awesome and helpful to expand other function that i wanna. By the way, I have a question about the range of input angle . This function uses the circularArray for generating random number by using cosine and sine trigonometric function. whatever angle is inputted, range of cosine and sine function is absolutely from -1 and 1.

So, this function can be used only for range of number between -1 and 1? or is there any other way to expand the range?

Thanks:)

kimandrik commented 6 years ago

Hello. We used circularArray just for testing. The most important thing for your input x is that |1 - x| < 1/2, i.e. x should be not far from 1 (That is the reason why we used small angle in the test). The constant 1/2 can be replaced by a larger constant, but in this case, the error will increase. Please, refer to the section 4.2 of https://eprint.iacr.org/2016/421.pdf for more details.