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I like crypto. Need I say more?


20m
comment Building a pad for OTP on-the-fly with Diffie-Hellman
OTP does not necessarily require an offline key exchange.
1d
comment Decrypt with only the cipher file and the key?
Hmm, based on the information you've given us, try every cipher/mode combination known to man (from the most probable to the least). Also known as, brute-force.
1d
comment Private Information Retrieval--Is it still theoretical?
Here is a library.
1d
comment Private Information Retrieval--Is it still theoretical?
Possible duplicate of crypto.stackexchange.com/questions/20389/…
1d
comment Real life systems that use concepts of crypto computing
List questions are often closed as off-topic here. There have been some exceptions. I'll let the community decide on this one.
1d
comment Real life systems that use concepts of crypto computing
Making this CW so that others can edit and add additional information more freely.
1d
answered Real life systems that use concepts of crypto computing
2d
comment Python. RSA common modulus attack problem
I am familiar with python and can give you a few pointers. First, with pow, pow supports a third parameter to compute modular exponentiation. So doing pow(a,b,n) computes, $a^b\bmod{n}$. For computing inverses, I typically use pycrypto (Crypto.Util.number.inverse).
Nov
20
comment Are all binary-additive stream ciphers reciprocal?
The inverse of XOR is XOR, so yes.
Nov
20
comment Is there a Javascript and Java implementation of a good CSPRNG
Why do they have to be the same algorithm? Could you run node.js on the server side? I think your question would be better off on a different site. This site is more about theoretical aspects of crypto. StackOverflow or IT Security could be better sites. If you want me to migrate the question, let me know.
Nov
20
comment To prove $r \cdot f_1 +f_2 \cdot (s+1)$ is secure
Trying to add/invite you. Are you the other person in the room?
Nov
20
comment To prove $r \cdot f_1 +f_2 \cdot (s+1)$ is secure
Let us continue this discussion in chat.
Nov
20
comment To prove $r \cdot f_1 +f_2 \cdot (s+1)$ is secure
Looking at Lemma 2, $r,s$ have degree $\beta$ where $\beta\geq\alpha$ where $\alpha$ is the degree of $f$ and $g$.
Nov
20
comment To prove $r \cdot f_1 +f_2 \cdot (s+1)$ is secure
Their Lemma 2 does specifically have that $degree(r)$ and $degree(s)$ $>$ $degree(f_1)$ (and $f_2$). Not sure if it can be extended to the case where $degree(r)=1$. Just checking, you do mean degree $1$ for $r$ and not $0$ (a random constant), right?
Nov
20
comment To prove $r \cdot f_1 +f_2 \cdot (s+1)$ is secure
Looking over that paper, they say that given $f*r + g*s$, where $f$ and $g$ are the polynomial representations of $S$ and $T$ respectively and $r$ and $s$ are random polynomials of degree $deg(f)$, the attacker learns no additional information about $S$ and $T$ than what can be deduced from $S\cap T$. Not sure how this directly translates to your problem.
Nov
20
answered To prove $r \cdot f_1 +f_2 \cdot (s+1)$ is secure
Nov
20
comment To prove $r \cdot f_1 +f_2 \cdot (s+1)$ is secure
One more question. Multiplying two polynomials increases the degree of the polynomial. Basically the degrees add. You aren't doing any dimensionality reduction step (like we typically see with shamir based MPC), are you?
Nov
19
comment Should I study advanced abstract algebra and more than elementary number theory to pursue a career in cryptography?
What do you mean by "a career in cryptography"? Do you know what it is you want to do?
Nov
19
comment homomorphic paillier cryptosystem vs Elliptic curve cryptosystem
Paillier is a very specific cipher. Elliptic curve cryptosystem is a very generic cipher. Do you mean elliptic curve elgamal (ECIES)?
Nov
18
comment Interactive assumptions not falsifiable?
Can you give us more context? Did you read this in a paper or book? A link to the material with relevant quotes pasted into the question would be very helpful.