instruction stringlengths 15 30k |
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I want implement an article that is about making secure biometric templates using fuzzy commitment. This schema is used in many papers. I'm wondering, is there any open source
<br>
implementation of this schema available? Especially in `matlab`? |
I've been taking a crypto course online. I have a good idea how PRG's and Stream Ciphers work, but I'd love to get some input to help visualize what is actually happening. I understand a seed is used, then expanded into a keyspace. Is this correct?
So: `G: {0,1}^s -> {0,1}^n , n >> s`
From what I understand.. Fo... |
I am asking for help in finding a signature algorithm with the following property:
1. Given a message `m` and a private key `k`, the result of signing `m` with `k` is unique (which is stricter than deterministic).
2. Space efficiency of storing private key and signature is important.
ECDSA's space efficiency ... |
I am asking for help in finding a signature algorithm with the following property:
1. Given a message `m` and a private key `prikey`, the result of signing `m` with `prikey` is unique (which is stricter than deterministic). In another word, there is only one signature (or finding another one using `prikey` is secur... |
I want implement an article that is about making secure biometric templates using fuzzy commitment and fuzzy vault .i need ti implement just fuzzy commitment:(fuzzy commitment is a biometric cryptosystem )
http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=6033044&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fab... |
I want implement some ideas from [an article](http://www.cse.msu.edu/biometrics/Publications/SecureBiometrics/NagarNandakumarJain_MultibiometricCryptosystems_TIFS11.pdf) that is about making secure biometric templates using fuzzy commitment and fuzzy vault. I need to implement just the fuzzy commitment (fuzzy commitmen... |
In general, we execute key-mixing, substitution and permutation sequentially in a single round in a n-round SPN, but if we execute n-round key-mixing firstly, n-round substitution secondly and n-round permutation finally, how is the security of this modified SPN? |
VKO GOST R 34.10-2001 was described in [RFC4357 Page 7][1]
But the description is very poor. Here it is:
<!-- language: lang-none -->
This algorithm creates a key encryption key (KEK) using 64 bit UKM,
the sender's private key, and the recipient's public key (or the
reverse of the latter pair).
... |
Is appending the hash of the plaintext to the end of an encrypted message sufficient to ensure integrity?
My reasoning is that the attacker doesn't know all the plaintext, so by having a hash, the attacker will be able to change the message, but will be unable to recalculate the hash.
Are there any flaws in my re... |
How can I get point addition equation for elliptic curves in projective co ordinate system? Can I get it by changing $$ x = X/Z $$ and $$ y =Y/Z $$ in the equation for affine co ordinates' group law?
I have done it using the above narrated step and made the denominator as $ Z $ in equation for binary super-singular ... |
I'm searching a definition of "generic attack" in context of cryptography or more specific in context of "hash functions". I searched some books and the web but I did not found any definition for it only the usage like "generic birthday attack".
Does someone have a definition for that or knows where I get one? |
Is there any definition for "generic attack" in context of cryptography or more specific "hash functions"? |
VKO GOST R 34.10-2001 was described in [RFC4357 Page 7][1]
But the description is very poor. Here it is:
> This algorithm creates a key encryption key (KEK) using 64 bit UKM, the sender's private key, and the recipient's public key (or the reverse of the latter pair).
> 1. Let $K(x,y,UKM) = ((UKM*x)(mod q)) . (y... |
If I'm encrypting very short/small data - like an int or a long (32 or 64 bits), does it make any sense to authenticate the ciphertext, when using an "online" mode of operation (like EAX)?
Essentially, guessing the plain text would (assuming no weaknesses in either the encryption or the authentication) be easier th... |
Is it possible (how difficult) to find MORE than one valid RSA signature? |
See here for the man-in-the-middle attack on Diffie-Helmman that I'm concerned about: http://www.emc.com/emc-plus/rsa-labs/standards-initiatives/what-is-diffie-hellman.htm
How do we combat this? I have two questions:
1) Is one solution for both Alice and Bob just using a certificate authority, then they can each... |
See here for the man-in-the-middle attack on Diffie-Hellman that I'm concerned about: [What is Diffie-Hellman?][1]
How do we combat this? I have two questions:
1. Is one solution for both Alice and Bob just using a certificate authority, then they can each look up the other's certificate and know the secret key w... |
The [question][1] Alex linked in comments explains why authentication works to prevent a man-in-the-middle attack on Diffie–Hellman. So, whenever you can do the key exchange in an authenticated channel, you can be sure there is no MitM attack. (Assuming DH problem remains unbroken, of course.)
Now, your questions:
... |
Practical techniques for searchable encryption proposed by Song et all [1] have a false positive rate of $l/2^m$ where $l$ is left half of encrypted bits and $m$ is right half and $l+m=n$ where $n$ is number of bits of the word being encrypted. For getting clarity on these bits please refer the figure 3 in page 6. [pap... |
Is it feasible to use combination of ABE schemes for encrypting the data? |
Basically CP-ABE (or attribute based encryption) allows end-users to encrypt the data with desired access control structure. I was trying to find if encrypted data support the search operation by third party provided the third party is given appropriate keys (may be like delegation keys). Interestingly the paper "Multi... |
I ran several benchmarks using `openssl` and on 2 different computers and I got a surprising result.
for the Nist 192 bit curve the benchmark result is
>openssl speed ecdsap192
sign verify sign/s verify/s
192 bit ecdsa (nistp192) 0.0001s 0.0003s 11980.6 34... |
Why is 224 bit ecdsa faster than 192 bit ecdsa? |
Basically CP-ABE (or attribute based encryption) allows end-users to encrypt the data with desired access control structure. I was investigating the how to do keyword-search on encrypted data given the user has appropriate keys (may be like trap-door/delegation keys).
Interestingly the paper "Multi-user Attribute B... |
Symmetric key encryption schemes have well defined modes of operations for achieving deterministic (ECB) or Randomized (CBC, OFB, CTR ) etc. and other applications of the same. But are they defined for public key encryption schemes also ? i could not find on google.
Also are they applicable for PKE schemes ? |
In many articles i have found directly the calculation of prime elliptic curve. How can i calculate this **prime** $p$ ? For example if I consider **NIST P-256**, $ p = 2^{256}-2^{224}+2^{192}+2^{96}-1$. Why ? Is there a formula ? Thanks for your support. |
How can i calculate prime of Elliptic Curve? |
This prime $p$ corresponds to the size on the base field $\mathbb F_p$ on which is defined the elliptic curve. It has not been computed, it has been chosen. It is chosen to satisfy a few properties, like, of course, being prime, but also being large enough (here, 256 bits), and allowing fast computations modulo $p$.
M... |
I ran several benchmarks using `openssl` on 2 different computers and I got a surprising result.
for the Nist 192 bit curve the benchmark result is
>openssl speed ecdsap192
sign verify sign/s verify/s
192 bit ecdsa (nistp192) 0.0001s 0.0003s 11980.6 3481.6... |
I need to do digital signing of my request data which will be sent to the server. My server sends distinct private keys to her clients after authentication and expects all responses to be digitally signed with that keys for next x days. In order to represent a private key instance in iOS it expects a .p12 file with a p... |
I need to do digital signing of my request data which will be sent to the server. My server sends distinct private keys to her clients after authentication and expects all responses to be digitally signed with that keys for next x days. In order to represent a private key instance in iOS it expects a .p12 file with a p... |
I've been taking a crypto course online. I have a good idea how PRG's and Stream Ciphers work, but I'd love to get some input to help visualize what is actually happening. I understand a seed is used, then expanded into a keyspace. Is this correct?
So: $G: \{0,1\}^s \to \{0,1\}^n , n \verb|>>| s$
From what I und... |
The real question isn't "Why doesn't Suite B use P-521?" It is, "Why doesn't Suite B use AES-192?" NSA were only interested in 192-bit security for Suite B, but they chose to use AES-256 because AES-192 wasn't widely supported.
> "In fact we had wanted to use AES -128 and AES-192, but a quick survey of AES implement... |
I need to do digital signing of my request data which will be sent to the server. My server sends distinct private keys to her clients after authentication and expects all responses to be digitally signed with those keys for next x days. In order to represent a private key instance in iOS it expects a .p12 file with a ... |
Doing malware research (simple crypto locker) I found out that it uses AES-128 with weak key - every of sixteen bytes is represented by (a-z,A-Z,0-9).Thus simple brute-force attack should iterate through pow(62,16),that is approximately pow(2,96). I have a file before encryption and after.
Is it feasible in modern wo... |
I have seen in few places (mostly papers) talking about plain cascade and XOR cascade. I know what is cascade cipher is but I am not clear about what these are. Can anyone help to understand using simple words to define what is a XOR cascade? (how XOR is involved in cascade cipher?) |
The notion of plaintext-awareness is well-known for asymmetric encryption, but the notion seems to make sense for symmetric encryption as well. Is this a known concept? |
Plaintext-aware encryption for symmetric schemes? |
How do I calculate the bounds of cascade cipher from this:(k detarmines keysize and n is the blocksize)
>exp( K+ min{k(l-2)/2}, n(l-2)/l}) , where l is the cascde length and l >1
If there is a cascasde of AES, Blowfish and DES then what will be the value of K? and what will be the value of n? is this just ... |
Doing malware research (simple crypto locker) I found out that it uses AES-128 with weak key - every one of the sixteen bytes is represented by (a-z,A-Z,0-9). Thus simple brute-force attack should iterate through $62^{16}$, that is approximately $2^{96}$ keys. I have a file before encryption and after.
Is it feasib... |
How do I calculate the bounds of cascade cipher from this:(k detarmines keysize and n is the blocksize)
>exp( K+ min{k(l-2)/2}, n(l-2)/l}) , where l is the cascde length and l >1
If there is a cascasde of AES, Blowfish and DES then what will be the value of K? and what will be the value of n? is this just ... |
I need to do digital signing of my request data which will be sent to the server. My server sends distinct private keys to her clients after authentication and expects all responses to be digitally signed with those keys for next x days. In order to represent a private key instance in iOS it expects a `.p12` file with ... |
I’m reading [*“The Security of Multiple Encryption in the Ideal Cipher Model”*](https://www.cosic.esat.kuleuven.be/publications/article-2443.pdf) and I’m having a hard time understanding something. How do I calculate the bounds of cascade cipher from the following formula (where $k$ determines keysize and $n$ is the b... |
Groth-Sahai framework enables us to commit to QE, MSME, PP equations. Now, is the equation below committable in GS framework?
A bilinear map $e: G_1 \times G_2 \rightarrow G_T$. $g_1 \in G_1$ and $g_2 \in G_2$ are the generators of the corresponding groups. $K \in G_1$ and $\tau \in G_T$ are constants. $x,y \in Z_p$... |
We all know there are five properties of Security. They are:
1. Confidentiality
2. Availability
3. Authorization
4. Integrity and
5. Provenance
As Security and Cryptography are co-related these properties also applicable to Cryptography as well (are't they?). I can understand how a Cryptographic algorithm... |
Would a DES algorithm that uses all 64 bits for the key instead of just the 56 bits be more secure? I have been thinking about it but those 8 bits used for parity are very useful and but including them in the key could potentially make it more easily cracked.
From Wikipedia, it stated that the 56 bit key was cracked... |
I'd like to use a curve that's not included in the Bouncy Castle EC named curves spec, specifically E-521.
According to the BC javadocs, you need a few values in order to do this: *q*, *a*, and *b* for the curve, then *G* and *n* for the parameter spec.
<!-- language: lang-java -->
import org.bouncycastle.... |
Would a DES algorithm that uses all 64 bits for the key instead of just the 56 bits be more secure? I have been thinking about it but those 8 bits used for parity are very useful and but including them in the key could potentially make it more easily cracked.
From Wikipedia, it stated that the 56 bit key was cracked... |
I was reading a [paper on the "elephant diffuser" used in BitLocker][1] and it got me wondering how other systems (e.g. TrueCrypt before it shutdown) solved the problem the elephant diffuser was meant to solve; namely that there isn't enough space on a disk block to store an IV. Where is the IV stored in other systems... |
How do disk encryption programs solve the "IV problem"? |
Is elliptic curve point multiplication semantically secure? I'd like to know if there are some sets of elliptic curve parameters (e.g. NIST curves) that are proved to be semantically secure or that are not disproved.
By "elliptic curve point multiplication is semantically secure", I mean the following:
Suppose an... |
Is elliptic curve point multiplication semantically secure? |
I was thinking of this since yesterday. Imagine, a secret is split into its respective shares (using any secret sharing scheme) with threshold $t$ and total $n$. Can we find out given any random string if it is a valid share of the secret ?
Of course without brute force approach, i.e splitting the secret into its ... |
I was learning about the finding the key length reading the following web site...
http://practicalcryptography.com/cryptanalysis/stochastic-searching/cryptanalysis-vigenere-cipher/
and I really don't understand some part of the example shown in the web.
They assume the key length is 2 and extract the two sequence ... |
I would like a data structure supporting two operations: set(k,v), and get(k), with the following properties:
1. k can be any number between 0 and something impressively large, like 2^256-1.
2. If there is some v such that set(k,v) has been called then get(k) returns the most recent such v.
3. There is no way to l... |
Just to be specific we are talking about information theoretically secure secret sharing, e.g. Shamir sharing. Lets say a secret $secret$ is shared in $n$ shares $S = \{s_1, \ldots, s_n\}$. Assume further party $P_i$ is given share $s_i$. If I understand your question correctly, you are asking if we give $P_i$ some sha... |
in $GF(2^8)$ the AES affine transformation is defined as
\begin{equation*}
b( x ) = ( x^7 + x^6 + x^2 + x ) + a ( x )( x^7 + x^6 + x^5 + x^4 + 1) mod (x^8 + 1)
\end{equation*}
where the polynom $( x^7 + x^6 + x^2 + x )$ represents the constant term and $( x^7 + x^6 + x^5 + x^4 + 1) mod (x^8 + 1)$ is the matrix, whi... |
Is there any consensus (i.e. are there any research results) on the benefits and drawbacks of various padding schemes?
Generally there seem to be two kinds of them:
* random paddings, like ISO10126 that pad with random data
* fixed paddings, like PKCS5/7 and X.923 that pad with 0s or some fixed pattern
Is the... |
in $GF(2^8)$ the AES affine transformation is defined as
\begin{equation*}
b( x ) = ( x^7 + x^6 + x^2 + x ) + a ( x )( x^7 + x^6 + x^5 + x^4 + 1) mod (x^8 + 1)
\end{equation*}
where the polynom $( x^7 + x^6 + x^2 + x )$ represents the constant term and $( x^7 + x^6 + x^5 + x^4 + 1) mod (x^8 + 1)$ is the matrix, whi... |
Using modulus in one time pad? |
I was learning about the finding the key length reading the following web site...
http://practicalcryptography.com/cryptanalysis/stochastic-searching/cryptanalysis-vigenere-cipher/
and I really don't understand some part of the example shown in the web.
They assume the key length is 2 and extract the two sequence ... |
I would like to know what is the real purpose of using a modulus in the equivalent of vernam's cipher:
data d, large number M
k <- [0, M-1]
Encryption: C = k + d mod M
Decryption: d = C - k mod M
What's the purpose of using M? |
It depends on what you think of as an alternative.
If you think of the scheme where you do not use M as a modulus, but the keys a picked as:
$$
k \leftarrow \{1, \ldots, M-1\}
$$
Encryption:
$$
C = d + k
$$
Decryption:
$$
d = C - k
$$
Then the scheme is insecure. One way to see this is to note that we... |
There are alternative representations of $GF(2^8)$ where the multiplicative inverse can be computed by computing the inverse in $GF(2^4)$, along with a handful of other operations (several $GF(2^4)$ multiplies, additions and a square). Does your $\delta$ convert from the standard AES representation into such an altern... |
There are alternative representations of $GF(2^8)$ where the multiplicative inverse can be computed by computing the inverse in $GF(2^4)$, along with a handful of other operations (several $GF(2^4)$ multiplies, additions and a square). Does your $\delta$ convert from the standard AES representation into such an altern... |
Is it possible to hand-negotiate an SSL/TLS session? |
There are alternative representations of $GF(2^8)$ where the multiplicative inverse can be computed by computing the inverse in $GF(2^4)$, along with a handful of other operations (several $GF(2^4)$ multiplies, additions and a square). Does your $\delta$ convert from the standard AES representation into such an altern... |
I don't blame whomever down-voted this, I realize now it was a stupid question.
In order to do this, first convert the Edwards curve to Montgomery form, then to Weierstrass form, per [this thread][1].
But, as the above thread explains, as well as CodesInChaos' comment, this will result in poor performance.
Tha... |
I was reading upon Biham and shamir's paper and a fact has been presented over there -
if $ P1 = \overline P2$ and I choose a key $K1 = \overline K2$ then in that case
$$T1 = DES(P1, K1)$$
$$T2 = DES(P2, K2)$$
then $T1 = \overline T2$ . Does this hold for only that particular combination of s box or it will be ... |
I would like to know what is the real purpose of using a modulus in the equivalent of a Vernam cipher:
data $d$, large number $M$
$k \leftarrow [0, M-1]$
Encryption: $C = k + d \mod{M}$
Decryption: $d = C - k \mod{M}$
What's the purpose of using $M$? |
There are alternative representations of $GF(2^8)$ where the multiplicative inverse can be computed by computing the inverse in $GF(2^4)$, along with a handful of other operations (several $GF(2^4)$ multiplies, additions and a square). Does your $\delta$ convert from the standard AES representation into such an altern... |
I would like a data structure supporting two operations: set(k,v), and get(k), with the following properties:
1. k can be any number between 0 and something impressively large, like 2^256-1.
2. If there is some v such that set(k,v) has been called then get(k) returns the most recent such v.
3. There is no way to l... |
I would like a data structure supporting two operations: set(k,v), and get(k), with the following properties:
1. k can be any number between 0 and something impressively large, like 2^256-1.
2. If there is some v such that set(k,v) has been called then get(k) returns the most recent such v.
3. There is no way to l... |
I would like a data structure supporting two operations: set(k,v), and get(k), with the following properties:
1. k can be any number between 0 and something impressively large, like 2^256-1.
2. If there is some v such that set(k,v) has been called then get(k) returns the most recent such v.
3. There is no way to l... |
I wonder what is the encryption scheme in these high-precision encrypted GPS streams (the so-called "P(Y) code". If there's a master key needed, then it has to be in every device. How come the key never leaked? |
Why military-precision channel GPS receivers still hasn't been hacked (like game consoles or Apple devices)? |
Short version: When generating a prime number of N bits, should I draw random numbers from the range [0 , 2^n], or [2^(n-1) , 2^n]?
Context: I'm trying to implement a toy-version of RSA as a hobby, with a Miller-Rabin test to generate primes. Initially, my function to generate the keys had the following signature:
... |
Generation of N bit prime numbers -> what is the actual range? |
I would like a data structure supporting two operations: set(k,v), and get(k), with the following properties:
1. k can be any number between 0 and something impressively large, like 2^256-1.
2. If there is some v such that set(k,v) has been called then get(k) returns the most recent such v.
3. There is no way to l... |
I would like to know what is the real purpose of using a modulus in the equivalent of a Vernam cipher:
Data $d$, large number $M$
Assume the key length is λ bits. Then M could be 2^λ.
k is picked from {0,1}^λ using a pseudo random function (PRF)
Encryption: $C = k + d \mod{M}$
Decryption: $d = C - k \mod{M... |
Short version: When generating a prime number of N bits, should I draw random numbers from the range $[0 , 2^n]$, or $[2^{(n-1)} , 2^n]$?
Context: I'm trying to implement a toy-version of RSA as a hobby, with a Miller-Rabin test to generate primes. Initially, my function to generate the keys had the following signat... |
Why haven't military-precision channel GPS receivers been hacked yet (like game consoles or Apple devices)? |
Is it possible to construct a zero knowledge proof that one encrypted number is larger (or not) than another encrypted number without releasing the values of either numbers? |
Is it possible to find out whether a number is greater than another number without knowing the numbers? |
Am I going to regret posting this? There seems to be enough non-classified information available about GPS to answer this question.
I see 3 reasons why P(Y) encryption is different and less likely to be hacked than game console encryption:
1. Hardware containing the GPS decryption key is more difficult to obtain ... |
Yes, it is possible. Actually, [any statement in NP can be proven in zero knowledge][1]. This means that if something can be proven by releasing some information, it is possible to prove the same without releasing any information, i.e. in zero knowledge.
[1]: http://dl.acm.org/citation.cfm?id=116852 |
Matthew Green states in the [Practical Kleptography presentation][1] (video, at about 12:15) that HASH_DRBG (from [SP800-90A][2]) as originally proposed by NSA was broken in an exploitable way and that NIST fixed it.
I've been unable to find how. [This VCAT report][3] only states that it was contributed by NSA and N... |
What weaknesses in HASH_DRBG did NIST find and fix? |
Matthew Green states in the [Practical Kleptography presentation][1] (video, at about 12:15) that Hash_DRBG (from [SP800-90A][2]) as originally proposed by NSA had potentially exploitable flaws or bugs and that NIST fixed it.
I've been unable to find how. [This VCAT report][3] only states that it was contributed by ... |
What weaknesses in Hash_DRBG did NIST find and fix? |
I recently noticed that opendkim on my mail server is objecting to DKIM signatures from a client, saying their key is insecure. It may be that that's due to lack of secure DNS (confirmation anyone?) but I also noticed that the signing algorithm is shown as a=rsa-sha1, and with the move to Deprecate SHA-1 in other conte... |
Deprecation of RSA-SHA-1 in DKIM keys? |
In Fully Homomorphic Encryption scheme represented here [Fully Homomorphic Encryption over the Integers][1]
In the Evaluate process
3.1 The Construction:
Evaluate(pk, C, c1, . . . , ct):
if I want to do some operations on an encrypted data, i should convert that operation to a binary circuit then do the oper... |
I would like to know the domains or specific applications where using AES-CBC is not advised due to any drawbacks like sequential encryption of AES-CBC ? |
Is there any area where AES-CBC cannot be used ? If so, why ? |
In Fully Homomorphic Encryption scheme represented here [Fully Homomorphic Encryption over the Integers][1]
In the Evaluate process
3.1 The Construction:
Evaluate(pk, C, c1, . . . , ct):
if I want to do some operations on an encrypted data, i should convert that operation to a binary circuit then do the oper... |
[CBC][1] is one of the five confidentiality modes. It needs one IV (Initialization Vector). The IV must be same length to the blocksize of the algorithm (e.g. 128bit for AES). The IV is done exclusive-ORed with the first plaintext block *P1*. The result of the first XOR operation is *C1*. Next *C1* is exclusive-ORed wi... |
I recently noticed that [OpenDKIM](http://www.opendkim.org/) on my mail server is objecting to DKIM signatures from a client, saying their key is insecure. It may be that that's due to lack of secure DNS (confirmation anyone?) but I also noticed that the signing algorithm is shown as `a=rsa-sha1`, and with the move to ... |
In Fully Homomorphic Encryption scheme represented here [Fully Homomorphic Encryption over the Integers][1]
In the Evaluate process (see section “3.1 The Construction” of the paper):
$$Evaluate(pk, C, c1, \dots , ct):$$
Now…
1. If I want to do some operations on an encrypted data, should I convert that operat... |
Many browsers and Internet companies have recently claimed that SSL Certificates with a signature algorithm of SHA1 will immanently no longer be considered secure. Most notably, [Google and Google Chrome](http://googleonlinesecurity.blogspot.com/2014/09/gradually-sunsetting-sha-1.html).
Yet I've read that since the... |
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