A question about Negative number multiplication about fullrns-heaan HOT 8 OPEN

Hi siaaron045

I tested as the following command.

// Encrypt mvec
Ciphertext cipher = scheme.encrypt(mvec, slots, L);

// Multiple negative value (= -0.1)
Ciphertext cmultCipher = scheme.multByConst(cipher, -0.1);
scheme.reScaleByAndEqual(cmultCipher, 1);

I checked the decrypted result. And It seems correct.
It would be better if you can attach some part of your code.

Best, Kyoohyung Han

from fullrns-heaan.

I test your code and the answer is right,
but when ''cipher'' is a negative number's ciphertext or make multiplication of two negative ciphertext,the answer is wrong.
like this:
//Encrypt mvec=-5 Ciphertext cipher1 = scheme.encrypt(mvec, slots, L); Ciphertext cipher2=cipher1; Ciphertext cmultCipher = scheme.multByConst(cipher1, -1); //or Ciphertext cmultCipher = scheme.mult(cipher1, cipher2); scheme.reScaleByAndEqual(cmultCipher, 1);
both of the answers are wrong.
So the encrypted number can't be negative?

from fullrns-heaan.

Oh... when I put -1 instead of -5 it works.

This problem came from the negate function in Context.cpp.
I will fix this problem soon.

Thanks for the report.

from fullrns-heaan.

Yes,but it works only when mvec=-1, i put -2,-3,-4 the answers are wrong.
And the function scheme.mult(cipher1, cipher2) does not work when make multiplication of two negative ciphertext expect -1.
Thanks.

from fullrns-heaan.

The error still exist.
I hope you can take some time to fix it.
Thank you.

from fullrns-heaan.

@KyoohyungHan Looks like you found the error source. Can you be more specific where is it? I think I can submit a patch.

from fullrns-heaan.

The error still exist. I hope you can take some time to fix it. Thank you.

Hi~ is this problem solved? I found the same error too,but i have no idea how to fix it?Where exactly does this problem occur?

from fullrns-heaan.

This problem is not because of the negate function, but because of a problem with encode, where for copying simply adding the modulus leads to an encoding error. You can fix it by referring to the encoding functions of OPENFHE or Lattigo.

from fullrns-heaan.