meta user
network profile
| bio | website | |
|---|---|---|
| location | ||
| age | ||
| visits | member for | 1 year, 3 months |
| seen | 19 mins ago | |
| stats | profile views | 29 |
|
May 2 |
comment |
Knowing a valid salted hash for an unknown secret, is it possible to compute another valid hash? @fgrieu: I see. Well, calling the new salt $x$ or $r'$ shouldn't technically matter. What would make my answer invalid, would be a restriction of the length of the salt part $r$ of $d$, or a restriction that if $d \neq d'$, then there doesn't exist a sub-exponential function $f$ that would allow the derivation of $r$ from $d'$ or $r'$ from $d$. |
|
May 2 |
answered | Knowing a valid salted hash for an unknown secret, is it possible to compute another valid hash? |
|
May 1 |
comment |
Why does key generation take an input $1^k$, and how do I represent it in practice? While it is correct that $k$ usually represents the amount of desired cryptographic strength is desired from the key generation algorithm, it seems it might represent any parameter that might cause some other aspect of the scheme to grow exponentially. Confer e.g. crypto.stackexchange.com/a/7853/1564 |
|
May 1 |
revised |
What does the expression $1^n$ mean as a function argument? added 223 characters in body |
|
May 1 |
comment |
What does the expression $1^n$ mean as a function argument? let us continue this discussion in chat |
|
May 1 |
revised |
What does the expression $1^n$ mean as a function argument? added 20 characters in body |
|
May 1 |
comment |
Perfect secrecy Proof Have you tried using a straight logical proof, using the definition $Pr(A|B) = Pr(A \& B)/Pr(B)$? |
|
May 1 |
revised |
What does the expression $1^n$ mean as a function argument? added 764 characters in body |
|
May 1 |
revised |
What does the expression $1^n$ mean as a function argument? added 764 characters in body |
|
May 1 |
comment |
What does the expression $1^n$ mean as a function argument? @D.W.: I think we should make a distinction between "valid attributes" and "numerically possible attribute values". I meant the former, istm you mean the latter. My point is that if you accept more than $2^n$ different attributes as valid in the sense that you accept more than $n$ predicates, you still can't use the numerical methods outlined in the paper for selecting attributes that combine more than $n$ predicates at a time - you will end up with an overdetermined equation system if you try to select an attribute for $n+1$ predicates. |
|
May 1 |
comment |
What does the expression $1^n$ mean as a function argument? @D.W.: Unless my math is completely off, there can't be $N^n$ possible disjoint attribute values, due to the way the predicates and attributes are combined, using a dot vector product in $\mathbb Z_N$. If the dot vector product evaluates to $0$, the predicate is "included" in the attribute. Assuming both attribute hiding and information theoretic security, the number of independent predicates and attributes are bounded by the number of linear equations that would be required to solve unknown predicates, which is $n$. |
|
May 1 |
comment |
What does the expression $1^n$ mean as a function argument? @D.W.: There is more to it. The parameter $n$ is not just an empty place holder that only exists in the security parameter $1^n$, but represents the number of dimensions in the formal attribute set $\mathbb Z_N^n$. Confer page 3. |
|
May 1 |
comment |
Perfect secrecy Proof How do you define "perfect secrecy"? As $Pr(m|c) = Pr(m)$? |
|
Apr 24 |
comment |
What does “securely realize” mean? Generally, if the author of the paper defines the meaning of that phrase or provides a footnote with a reference, the phrase is intended to have specific technical meaning, otherwise probably not. |
|
Apr 23 |
answered | Using the same secret key for encryption and authentication in a Encrypt-then-MAC scheme |
|
Apr 22 |
answered | Is it possible to work out the hash algorithm from a list of known message-hash pairs? |
|
Apr 21 |
comment |
Is encrypting a single 128 bit block with AES ECB “safe” The latter, but it is an intriguing question on its own. Is it generally possible to break collision resistance of a Merkle-Damgaard chaining of a Davies-Meyer construct that is built around a compression function that is not pseudo random? |
|
Apr 20 |
comment |
Chain several RSA encryptions without increasing the message size @user2301771: Sorry, but you still haven't explained why you are asking (which IMO is important in order to give an adequate reply). Is it out of purely theoretical-mathematical interest, or is this something you actually want to do in practice? In the latter case, why? |
|
Apr 20 |
comment |
Is encrypting a single 128 bit block with AES ECB “safe” SHACAL-2 (i.e. the compression function of SHA-256) is a block cipher with a 256 bit block, which was approved e.g. by NESSIE. FWIW, considering the security proof of the Davies-Meyer construct, I presume SHACAL-2 might be assumed to be a secure block cipher if SHA-256 might be assumed to be a CSOWHF. |
|
Apr 20 |
comment |
Chain several RSA encryptions without increasing the message size If you want any kind of suggestion about what would be secure to do, you have to explain exactly why you want to RSA encrypt some RSA cipher text. If I may guess you are either trying to invent some kind of counter signature scheme, or are using RSA in a block chaining mode, in both cases for which there are other recommended practices. |
