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Jul
10
comment Hardness of finding mutual discrete logarithms of small generators in $\mathbb{Z}_p$
@Pierre: (Generalized) Tonelli-Shanks is an algorithm for finding (arbitrary) roots in cyclic groups. It's not the same thing, far from it, but if you see a connection, please feel free to demonstrate it.
Jul
3
comment Working on subgroup of $\mathbb{Z}^*_p$ in practice
It is important to know in exactly what sense you "need to work on some elements not in the subgroup". Your question does not include any reference to any cryptographic scheme or algorithm.
Jul
3
comment Working on subgroup of $\mathbb{Z}^*_p$ in practice
It is unclear what you are asking. Are you asking what role large multiplicative subgroups play in cryptography, or do you simply want to know more about the algebraic properties of the fields and groups involved?
Jul
3
comment Easy explanation of “IND-” security notions?
No, I don't think it is a duplicate. You will not necessarily understand the precise meaning of IND-CPA just because you know what is meant by a Chosen Plaintext Attack, etc
Jul
1
comment Deriving HMAC key and cipher key from passphrase?
@mistika: It depends on which algorithms you use for the generic EtA composite scheme. In some cases your scheme will break down completely if you use the same key for both (e.g. if you combine AES-CBC for confidentiality with AES-CBC-MAC for authentication). In other cases the algorithms are likely different enough for there not to be any practical attacks, should you use the same key for both components. However, you can't prove that the generic composition by itself is as secure as the least secure component, unless your premise is that the components use independent keys.
May
9
comment Difference between “Signature Algorithm” and “Signature Hash Algorithm” in X.509
RSASSA-PSS is a completely different beast altogether. A correct representation would require not only Signature Algorithm and Signature Hash Algorithm, but also identifiers for MGF Algorithm and P Source. This is however beside the point.
Mar
9
comment Will SHA1 or Other Hash Functions Ever Contain Quotes
I'm voting to close this question as off-topic because this is an apples and oranges kind of question. SHA-1 will output a string of 160 bits. A quote character is a character and not a bit. Your question will only make sense, if there is an implied conversion algorithm from the bit string output of SHA-1, to the character string you store in your database. This conversion algorithm might be chosen independently of the hash algorithm. Hence, your question is off-topic.
Feb
17
comment How many attempts does it take to crack a 32-bit password hash with this scenario?
Could you explain, in pseudo-code, exactly what you mean by "attempts" in the context of "matching a 32-bit hash from 4 million hashes". Finding a value that is known to exist in a list of 4 million values, depends on whether the list is already sorted or not, and does not depend of what kind of values are in the list or how they were generated.
Feb
16
comment ECC considered secure in OpenSSL?
The term "safe curve" seems to be used by Bernstein for curves that meet certain criteria, selected to make it easy to ensure that simple implementations are secure implementations. This doesn't imply that "non-simple" implementations using other curves are not secure. Hence, the information provided on the page is insufficient to infer anything about the security of OpenSSL, although it does raise some flags.
Jan
7
comment Do I have to transfer the private key to digitally sign a remote document?
If anything is preventing you from transmitting the unsigned pdf back to the client for signing, I am afraid the problem is with your requirements. You will either need some basic pdf parser client side, or you will have to let the server sign the document using a certificate that is not issued for the client. You can't have it both ways.
Dec
30
comment Do I have to transfer the private key to digitally sign a remote document?
Transfer the preliminary pdf to the client, let the client sign it and upload it back to the server. Alternatively, let the server sign it with a key corresponding to a certificate that belongs to the service rather than the user.
Dec
29
comment Do I have to transfer the private key to digitally sign a remote document?
What exactly does "DSC" mean in this context?
Dec
26
comment Prime Numbers in Discrete Log
You have chosen the tag "dsa", but there is no mention of digital signatures in your question. Do you need primes for Diffie-Hellman or for a signature scheme?
Dec
26
comment Which Block cipher mode should I use?
Define "secure".
Dec
15
comment What is difference between PRG, PRF, and PRP
Well, a poly-time observer has a relatively realistically good shot at distinguishing a few TB of a AES-CTR stream from a HMAC-MD5-stream, but not at distinguishing AES with a random key from a random permutation.
Nov
17
comment Key generation in Digital Signature Algorithm
The exact algorithm for generating the primes is specified in the DSS NIST FIPS 186-4 nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.186-4.pdf
Nov
15
comment Why we can't implement AES 512 key size?
"since AES-128 is safe enough for anything foreseeable" ...except when the cryptosystem is re-keying sufficiently frequently for collisions in the key space to become a concern.
Oct
3
comment What does OIW stand for
books.google.se/…
Oct
3
comment What does OIW stand for
Open System Implementors Workshop alvestrand.no/objectid/1.3.14.html
Sep
23
comment Is it possible to find out whether a number is greater than another number without knowing the numbers?
Do you need to compare each number in a pair only once, or multiple times?