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15h
comment Why don’t all AES encryption tools produce the same key from the same password?
For a tool, use GPG.
16h
comment One-time-pad with multiplication
If there is no decryption routine, is it really encryption? I think more context would be helpful? What security do you need? Just confidentiality?
17h
comment One-time-pad with multiplication
This question is somewhat related.
17h
comment One-time-pad with multiplication
How do you do the inverse operation?
19h
comment Looking for C++/Python Open Source code library for cryptanalysis of classical ciphers
@MosheRubin not sure what "email to the moderator" you are talking about. Care to explain?
1d
comment One time pad in CBC mode?
@Stefan: to add to what poncho says about impossibility. Correctly implemented OTP has a new pad every time. So, if I know the plaintext, I can get the pad, but that pad is never used again, so who cares. Same with CPA.
1d
comment One time pad in CBC mode?
But how do you do CBC (which is for fixed length block ciphers) with OTP (which is an infinite length stream cipher)?
1d
comment One time pad in CBC mode?
Is that what you are proposing doing?
1d
comment One time pad in CBC mode?
It is unclear from your question how that would even work. CBC mode is used to take a fixed length block cipher and turn it into something that can encrypt larger messages. OTP is infinite length. Are you suggesting dividing up the plaintext into chunks and propagating cipher text somehow? Perhaps some equations would be helpful. For example, say you divide the plaintext and the key stream into 128 bit chunks. Let $p_0$ be the first 128 bits of plaintext and $k_0$ be the first 128 bits of key stream. Then $c_0=p_0\oplus k_0$. Then for all $i>0$, $c_i=p_i\oplus k_i\oplus c_{i-1}$.
1d
comment Building a combined encryption scheme from two encryption schemes that's secure if at least on of them is secure
@gordon, the answer is, you can't delete this question. StackExchange is not a site to come to looking for answer and then delete them so that no one else can find them.
May
24
comment Executing encrypted code?
crypto.stackexchange.com/questions/1710/…
May
24
comment Common Modulus Attack in RSA
@rex don't forget to mark this as the answer by clicking the green check.
May
22
comment When to use RSA and when ElGamal asymmetric encryption
@Ragnagord also, if someone found a way to show that P=NP, that would not necessarily be a nail in the crypto coffin. See cases 2 & 3 of this answer.
May
22
comment When to use RSA and when ElGamal asymmetric encryption
@Ragnagord, right, but a break in RSA does not imply that P=NP. In other words, you could break RSA and still not know if P=NP. Your first comment says that breaking RSA involves proving that P=NP. That is not true.
May
22
comment When to use RSA and when ElGamal asymmetric encryption
@Ragnagord, Factoring is not known to be np-complete. So breaking RSA does not involve proving P=NP. This section of wikipedia is pretty good.
May
14
comment Protocol for signing and timestamping documents for e-archive system
I'm going to migrate this to IT Security. This site is more about theoretical aspects of cryptography. The IT Security site deals with (among other things) practical aspects of cryptography.
May
14
comment Why cant Public Key Encryption be perfectly secure?
What makes you think they can't? Just because we don't know of one that does, does not mean that one does not exist. I am not aware of any proof stating that a public key cipher cannot provide perfect secrecy. Are you?
May
13
comment Outsourced Multiparty computation proof in Ideal world
The start of section 4 of the paper you linked to has a pretty good explanation.
May
13
comment Outsourced Multiparty computation proof in Ideal world
you need to design the simulator in order to prove security. See this answer
May
12
comment Is HMAC-MD5 still secure for commitment or other common uses?
I updated the answer I referenced that had $hmac(m,k)$ to be $hmac(k,m)$