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Jan
5
reviewed Approve Why is the private key generated first in public key crypto?
Jan
5
answered Why is the private key generated first in public key crypto?
Dec
29
comment Formal proof of theorem concerning the Random Oracle Model
It's obvious. Recall that choosing a random function is equivalent to choosing the function values independently, one at a time.
Dec
23
comment Which multiplicatively homomorphic encryption scheme supports encryption of 0?
If you can live with $\{0,1\}$ as the message space, use any additively homomorphic scheme with a large message space and interpret encryptions of zero as $1$, and encryptions of anything else as $0$. Note that if you combine a ciphertext with itself a random number of times, this does not change the interpreted value of the ciphertext. To "multiply" two ciphertexts, randomize them (as above) and combine them.
Dec
22
comment Protecting a short password
Clarify your question, then add a n choose k. By the way, if you replace bytes in the Base64 expansion, you should use 6 above, not 8.
Dec
21
answered Protecting a short password
Dec
21
answered Which multiplicatively homomorphic encryption scheme supports encryption of 0?
Dec
21
comment Can a cryptosystem be unconditional secure if the same key $k \in \mathcal K$ is used for more than one encryption?
This isn't actually unconditionally secure unless you have state. Without a state, you may end up reusing key material.
Nov
9
reviewed Approve How do public key rings work in cryptographic applications?
Oct
20
comment Security proof of FO(Fujisaki-Okamoto) hybrid encryption
ECIES. RSA-KEM.
Sep
11
comment Proof for composed signatures
If $\epsilon_3$ is smaller than all three of $\epsilon$, $\epsilon'$ and $\epsilon''$, it will be smaller than the minimum, not the maximum...
Sep
9
answered How do you create a large PRP from a small one?
Sep
7
reviewed Approve How does one calculate the scalar multiplication on elliptic curves?
Sep
4
comment Proof for composed signatures
You have $\epsilon_3 \leq \epsilon$, $\epsilon_3 \leq \epsilon'$ and $\epsilon_3 \leq \epsilon''$. Can you find a smaller bound?
Aug
30
comment Proof for composed signatures
Recall that a scheme is $\epsilon$-secure if any adversary has advantage at most $\epsilon$. For any $\epsilon_3$-forger (adversary with advantage $\epsilon_3$) against the composed system, we get an $\epsilon_3$-forger against any of the three systems. Now we apply the definition of secure.
Aug
28
answered Proof for composed signatures
Aug
2
awarded  Yearling
Jul
31
comment Rainbow table for DES with all-zero plaintext?
No, $L$ chains of length $k$; checking if we are in a chain requires computing $k$ sequences of average length $k/2$.
Jul
31
revised Rainbow table for DES with all-zero plaintext?
The first version explained a random time-memory-data trade-off, not rainbow tables.
Jul
25
reviewed Approve AES mixcolumn stage