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10h
comment Common Modulus Attack in RSA
@rex don't forget to mark this as the answer by clicking the green check.
1d
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.
1d
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.
1d
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
18
comment Encrypting a file so that it can be decrypted everywhere out of the box
What is the problem you are trying to solve here? Define "restricted access". Because if the computer/phone has software whitelisting, then whatever you do would require that the software be installed on those machines. That significantly limits you. On the other hand, if you mean you can run anything that does not require admin access (not sure what this means on a phone, but that is understandable for a library computer), then you should be able to use most software out there.
May
15
awarded  cryptanalysis
May
15
revised How do we guarantee plaintext is coprime in RSA?
added 283 characters in body
May
15
answered How do we guarantee plaintext is coprime in RSA?
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 $hmac(k,m)$
May
12
revised Game with symmetric key
edited body
May
12
awarded  Guru
May
12
comment Is HMAC-MD5 still secure for commitment or other common uses?
@MaartenBodewes, hopefully only to the trained eye.
May
12
comment Role of trusted party in the Ideal model in Malicious case
What is your end goal? To prove security? If so, what is the high level strategy for this? Typically it is to show indistinguishability between the real world and the ideal world. Is that what you want to do?
May
11
asked Is HMAC-MD5 still secure for commitment or other common uses?
May
11
revised Is HMAC-MD5 considered secure for authenticating encrypted data?
edited title
May
11
comment Is HMAC-SHA-1 secure?
You should update your answer. An attack on HMAC-MD5 has been found.