HW6 Q1

HW6 Q1

Shlomi (guest) 16 Jan 2018 23:32

I am confused about correctness of the encrytpion scheme.

For example, if we encrypt message m=1 using sample e=0, when decrypting we get:

m' = -m mod q mod 2 = -1 mod q mod 2 = q-1 mod q mod 2 = q-1 mod 2 = 0
=> m' != m

What am I missing?

Re: HW6 Q1

nbitansky 17 Jan 2018 09:28

You're not missing anything. It should be "a slightly different mod q" —- the representative in $[-(q-1)/2,(q-1)/2]$ and not in $[0,q-1]$.

Re: HW6 Q1

nbitansky 17 Jan 2018 11:43

Also a bound on $B$ was missing.

Evyatar (guest) 31 Jan 2018 14:05

Is $\chi$ between 0 and $B$ or between $-B$ and $B$?

nbitansky 31 Jan 2018 14:44

In $[-B,B]$ as we defined in class.