instruction stringlengths 15 30k |
|---|
"Not vulnerable" is not how I would describe it, but my understanding is that the existing attacks on DES cannot directly not work with 3DES.
At the moment, the best attack against single DES is a linear attack which requires $2^{43}$ plaintext-ciphertext pairs, and has a time complexity of at between $2^{39}$ and $... |
I am wondering how much hashing a password used as key for a symmetric key algorithm helps preventing brute force attack on crypted text.
Let's assume I want to crypt text A using key B using AES-256. I expect user to input not secure keys, such as: `['apple', '22march', 'newyork']`.
So I hash these keys with PBK... |
> Would this help preventing brute force attacks?
It would slow down an attacker and prevent them from trying as many password guesses. E.g. if you used 1000 rounds like in RFC 2898, you would reduce the number of guesses by a factor of 1000.
Assuming you count dictionary attacks under brute force attacks, such a... |
I know most people around here (including myself) are anti-FIPS, but I have a FIPS related question.
Could a crypto system that is not FIPS, e.g. one based on primitives like Curve25519, achieve FIPS compliance if it is capable of upgrading to FIPS algorithms/implementations in a way that is complete. By complete I ... |
Could a crypto system that uses non-FIPS crypto but then upgrades complete to FIPS be FIPS certified? |
How do I calculate the number of computations needed to break SHA256 in case we are using it for safely storing passwords (togheter with a salt)?
Are there any formulas that can be employed?
For example:
>Passwords are chosen to be 5-character strings composed of lowercase latin letters and numbers, and are sto... |
I have confusion on Feistel word in key size.
Means, "what is the meaning of key size with different feistel word ?"
What does m=2,3,4 represent. |
What is the difference between a PRF and a PRF+? I am understanding them to mean the same thing, but I imagine that is because I don't understand their differences.
The [IKE RFC][1] defines a PRF as:
> This pseudorandom function (PRF) takes as input a secret, a seed, and
an identifying label and produces an... |
What is the difference between a PRF and a PRF+? |
This may seem like crypto 101, but why do hash functions like SHA2 and Whirlpool have round constants that are absorbed into their respective states?
I can understand that in a cipher you need some way to incorporate a variable secret key, but there are no such user keys for hash functions. All the round constants ... |
Why have round constants in hashes? |
I watched a [video][1] on Khan Academy explaining the Diffe-Hellman exchange. When I try to do an example problem, I get 1 all the time. Does the generator and prime modulus (or base on Wikipedia) have to somehow be related for the key exchange to work?
Here is my example:
Generator: 47
Prime modulus: 23... |
I watched a [video][1] on Khan Academy explaining the Diffe-Hellman exchange. When I try to do an example problem, I get 1 all the time. Does the generator and prime modulus (or base on Wikipedia) have to somehow be related for the key exchange to work?
Here is my example:
Generator: 47
Prime modulus: 23... |
How do I calculate the number of computations needed to break SHA256 in case we are using it for safely storing passwords (togheter with a salt)?
Are there any formulas that can be employed?
For example:
>Passwords are chosen to be 5-character strings composed of lowercase latin letters and numbers, and are sto... |
I have a question about security of FE1 in paper ["format preserving encryption"](https://eprint.iacr.org/2009/251.pdf). Can anyone explain me, why we are allowed to replace PRF with random function in security proof? And also, why G0 is equal to SPI1 and G1 is equal to SPI0?
|
I have a question about security of FE1 in paper ["format preserving encryption"](https://eprint.iacr.org/2009/251.pdf). Can anyone explain me, why we are allowed to replace PRF with random function in security proof? And also, why $G_0$ is equal to $SPI_1$ and $G_1$ is equal to $SPI_0$?
|
The PKCS #1 v2.0 suggests using lambda(n). What is the benefit of choosing lambda(n) over phi(n) in RSA key generation? |
The [PKCS #1 v2.0](https://www.ietf.org/rfc/rfc2437.txt) specifications suggest using $\lambda(n) = \mathrm{lcm}(p-1,q-1)$. What is the benefit of choosing $\lambda(n)$ over $\varphi(n) = (p-1)(q-1)$ in RSA key generation? |
I've been looking for a paper on this, but haven't found one. It's something that seems to be easy to check (in "On the Design of S-Boxes", Webster & Tavares lay out how it can be done), so it is surprising to not find a paper on it. Has it been put down as a small result in some other paper? Or has the SAC been dis... |
Does SHA-1 meet the strict avalanche criterion? |
Does SHA-1 meet the strict avalanche criterion? I've been looking for a paper to cite on this, but haven't found one.
It's something that seems to be easy to check (in ["On the Design of S-Boxes"](http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.41.8139&rep=rep1&type=pdf), Webster & Tavares lay out how it ca... |
While reading [Evaluation of Some Blockcipher Modes of Operation][1] by Rogaway (someone just linked it somewhere), I noticed two claims about CFB that I'm not sure I understand:
1. Regarding whether CFB mode encryption is parallelizable the paper says (on page 31):
> Yes, but awkward. See ISO 10116 for less awkwa... |
Does SHA-1 meet the strict avalanche criterion? I've been looking for a paper to cite on this, but haven't found one.
It's something that seems to be easy to check (in ["On the Design of S-Boxes"](http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.41.8139&rep=rep1&type=pdf), Webster & Tavares lay out how it ca... |
My goal is to allow two clients to send files securely over an untrusted network without the need for more than one block of information to be sent. Both clients have ECDSA keys of size 256 bits. I'd like to stress that this is purely for fun and to learn elliptic curve concepts. This will not be used in a serious envi... |
Is this a secure method of encrypting with authentication? |
Pallier Cryptosystem is probabilistic in nature and IND-CPA secure. By design given two ciphertexts one cannot distinguish whether decrypting those two ciphertexts will result in same or different plaintexts.
But in certain situations like Onion-layered encryption in CryptDB. There are other onions like DET and OPE... |
Pallier Cryptosystem is probabilistic in nature and IND-CPA secure. By design given two ciphertexts one cannot distinguish whether decrypting those two ciphertexts will result in same or different plaintexts.
But in certain situations like Onion-layered encryption in CryptDB. There are other onions like DET and OPE... |
Do quantum computers have any affect on the ability to solve the non-linear AES s-box algebraic expression, or does solving it still fall under search algorithms (Grover's)? If quantum computer do help solve it, what affect does this have on AES given that finding the key is still a brute-force search? |
I am currently having a look at J-PAKE , so learning about Authenticated Key Exchange :
Reading 2.2.2 E.K.E from this paper https://people.kth.se/~maguire/Erik_Ehrlund_Literature_Study_report_v1.2.pdf
I understand the use of PSK to authenticate a DH handshake.
question are :
*Is TLS DH ciphersuite based on PSK i... |
I am currently having a look at J-PAKE , so learning about Authenticated Key Exchange :<br>
Reading 2.2.2 E.K.E from this paper https://people.kth.se/~maguire/Erik_Ehrlund_Literature_Study_report_v1.2.pdf<br>
I understand the use of PSK to authenticate a DH handshake.
The question is :
**Is TLS DH ciphersuite b... |
I am currently having a look at J-PAKE , so learning about Authenticated Key Exchange :<br>
Reading 2.2.2 E.K.E from this paper https://people.kth.se/~maguire/Erik_Ehrlund_Literature_Study_report_v1.2.pdf<br>
I understand the use of the password to authenticate a DH handshake.
The question is :
**Is TLS DH ciph... |
Assuming you're actually asking wether there is a difference for TLS in between a (high-entropy) pre-shared key (PSK) and a (low-entropy) pre-shared password, the short answer is:
No.
The long answer, however is a bit more complicated.<br>
By itself the TLS-PSK ciphersuites don't differentiate between different ... |
Factorization of integers is hard, but finding irreducibles is expensive. Is there a ring where factorization is assumed hard but finding irreducibles is much cheaper than over $\Bbb Z$?
It could provide an alternative ring to do RSA/Rabin over. |
Are there UFDs where the factorization problem is difficult but finding irreducibles is cheap? |
Factorization of integers is hard, but finding irreducibles is expensive. Is there a ring where factorization is assumed hard but finding irreducibles is much cheaper than over $\Bbb Z$?
It could provide an alternative ring to do RSA/Rabin over.
___
A suggestion is the polynomial ring over $\Bbb Z_{pq}$ where ... |
Factorization of integers is hard, but finding irreducibles is expensive. Is there a ring where factorization is assumed hard but finding irreducibles is much cheaper than over $\Bbb Z$?
It could provide an alternative ring to do RSA/Rabin over.
___
A suggestion is the polynomial ring over $\Bbb Z_{pq}$ where ... |
Factorization of integers is hard, but finding irreducibles is expensive. Is there a ring where factorization is assumed hard but finding irreducibles is much cheaper than over $\Bbb Z$?
It could provide an alternative ring to do RSA/Rabin over.
___
A suggestion is the polynomial ring over $\Bbb Z_{pq}$ where ... |
IND-CPA is used to protect against frequency analysis AFAICT. But if RSA is only used to encrypt symmetric keys (AFAICT) then what's wrong with using only textbook RSA because random keys are very unlikely to repeat? |
If RSA is only used to encrypt symmetric keys which are random, what's wrong with textbook RSA? |
I am developing an application that is based on UDP, and I need to send a stream of packets. As you can imagine, packets can get lost or corrupted. I need to make sure that the content of those packets is encrypted, and I also need to be able to certify that the packet is correct when I receive it.
Finally, since p... |
IND-CPA is used to protect against frequency analysis AFAICT. But if RSA is only used to encrypt symmetric keys (AFAICT) then what's wrong with using only textbook RSA because random keys are very unlikely to repeat? |
The "interesting" part of your encryption is here:
> Therefore, I prepend a block at the beginning of my packet. Its content goes as follows:
>* First four bytes: current timestamp in seconds
* Next 12 bytes: zeros
* I compute the sha256 hash of the message (32 bytes)
* I xor the timestamp + zeros block with t... |
This is a common mistake, so I'd like to give an in-depth answer. Basically, what you are proposing is to rely on the ONE-WAYNESS of RSA as a ONE-WAY FUNCTION, rather than relying on its CPA or CCA security as an encryption scheme. The advantage of using RSA as a one-way function is that no padding etc is needed.
No... |
I am really not much of a crypto guy so I don't really get how a differential power analysis on AES works.
Can somebody explain it to me how it basically works or provide some easy understandable links for cryptography newbies for further readings?
|
I think we are all aware of the [CAESAR-competition][1]. Now the aim of this competition is to select a (portfolio of) winner(s) which provide authenticated encryption.<br>
I'll now assume that the results produced by this competition are *very* good, meaning the cryptanalysis of the next 50+ (!) years won't yield any... |
Can there be a need for 1024-bit (symmetric) encryption? |
How does DPA work on AES? |
I am really not much of a crypto guy so I don't really get how a differential power analysis on AES works.
Can somebody explain it to me how it basically works?
|
For example, if $m = 10011$, $k = 11001$, $n=3$ (which is the number of 1's in k), $c = m \oplus k = 01010$. If $c$ and $n$ are revealed to the attacker, is this scheme still secure? |
Is one-time-pad still secure if the number of 1's in the key is revealed to the attacker? |
I think we are all aware of the [CAESAR-competition][1]. Now the aim of this competition is to select a (portfolio of) winner(s) which provide authenticated encryption.<br>
I'll now assume that the results produced by this competition are *very* good, meaning the cryptanalysis of the next 50+ (!) years won't yield any... |
Can there be a need for 1024/2048-bit (symmetric) encryption? |
I think we are all aware of the [CAESAR-competition][1]. Now the aim of this competition is to select a (portfolio of) winner(s) which provide authenticated encryption.<br>
I'll now assume that the results produced by this competition are *very* good, meaning the cryptanalysis of the next 50+ (!) years won't yield any... |
I am currently learning, and I'm stuck on something that I thought is very simple. On many academic sources they suggest using Extended Euclidean Algorithm to calculate the multiplicative inverse for calculation of the S-Box, but I could not find a proper explanation how to do that. Every practical approach calculates ... |
I think we are all aware of the [CAESAR-competition][1]. Now the aim of this competition is to select a (portfolio of) winner(s) which provide authenticated encryption.<br>
I'll now assume that the results produced by this competition are *very* good, meaning the cryptanalysis of the next 50+ (!) years won't yield any... |
Can there be a need for 1024-bit (symmetric) encryption? |
This is a common mistake, so I'd like to give an in-depth answer. Basically, what you are proposing is to rely on the ONE-WAYNESS of RSA as a ONE-WAY FUNCTION, rather than relying on its CPA or CCA security as an encryption scheme. The advantage of using RSA as a one-way function is that no padding etc is needed.
No... |
I am completely new to using AES in GCM mode of operation, and I have not a very large background in cryptography as well. I have been playing with OpenSSL trying to encrypt and decrypt some messages. From my simple experiments rise the following questions:
- First of all, I noticed that the size of the output is e... |
Homomorphic encryption is hyped by computer sciences because it offers great potentials. For example you can perform cloud based calculation while nobody gets to know you data.
I am wondering if there is any homomorphic encryption scheme that is CCA secure. Can't you always just choose a random message, encrypt it ... |
Are all homomorphic encryption schemes not CCA secure? |
In order to answer this question, we need to understand the basis behind all of modern cryptography, which is _computational hardness_. Today, we believe that we know how to construct block ciphers that are secure, except for brute force search (or almost that secure). However, we don't really know this. We also think ... |
I am currently learning, and I'm stuck on something that I thought is very simple. On many academic sources they suggest using Extended Euclidean Algorithm to calculate the multiplicative inverse for calculation of the S-Box, but I could not find a proper explanation how to do that. Every practical approach calculates ... |
This is a common mistake, so I'd like to give an in-depth answer. Basically, what you are proposing is to rely on the ONE-WAYNESS of RSA as a ONE-WAY FUNCTION, rather than relying on its CPA or CCA security as an encryption scheme. The advantage of using RSA as a one-way function is that no padding etc is needed.
No... |
In order to answer this question, we need to understand the basis behind all of modern cryptography, which is _computational hardness_. Today, we believe that we know how to construct block ciphers that are secure, except for brute force search (or almost that secure). However, we don't really know this. We also think ... |
This is a common mistake, so I'd like to give an in-depth answer. Basically, what you are proposing is to rely on the ONE-WAYNESS of RSA as a ONE-WAY FUNCTION, rather than relying on its CPA or CCA security as an encryption scheme. The advantage of using RSA as a one-way function is that no padding etc is needed.
No... |
This is a common mistake, so I'd like to give an in-depth answer. Basically, what you are proposing is to rely on the ONE-WAYNESS of RSA as a ONE-WAY FUNCTION, rather than relying on its CPA or CCA security as an encryption scheme. The advantage of using RSA as a one-way function is that no padding etc is needed.
No... |
I am completely new to using AES in GCM mode of operation, and I have not a very large background in cryptography as well. I have been playing with OpenSSL trying to encrypt and decrypt some messages. From my simple experiments rise the following questions:
1. First of all, I noticed that the size of the output is ... |
I know the public modulus is the product of two primes. For key with length `L`, the public modulus `N` should be such `2^(L-1) <= N < 2^L`.
However this implies that the most significant bit will be always `1`. Doesn't this reduce the search space for the primes `P` and `Q` by half?
Shouldn't `N` be between `2^(... |
> Doesn't this reduce the search space for the primes `P` and `Q` by half?
I can't see how it does. After all the attacker can see $N$, and so can determine what bits are set. Allowing, say, a 2047 bit composite (rather than a 2048 bit) doesn't make his job any harder; he can see whether the composite in front of ... |
My goal is to allow two clients to send files securely over an untrusted network without the need for more than one block of information to be sent. Both clients have ECDSA keys of size 256 bits. I'd like to stress that this is purely for fun and to learn elliptic curve concepts. This will not be used in a serious envi... |
I understand that initialization vectors should not be used twice when using AES/GCM. I am using a counter as initialization vector. Every time I send out a new packet (I am developing an UDP based protocol that needs packet encryption) I increment the counter and use it as IV.
However, since I will generally need ... |
How bad it is using the same IV twice with AES/GCM? |
A FAQ for an open source project [makes the claim](https://electrum.orain.org/wiki/Frequently_Asked_Questions#How_secure_is_the_seed.3F):
>Indeed, an elliptic curve key of length n provides n/2 bits of security.
I have two questions:
1. What is the practical difference between "bits of entropy" and "bits of se... |
How many bits of entropy does an elliptic curve key of length n provide? |
The assumption for all cryptographic operations is that a random key of n bits has n bits of entropy. If it doesn't (due to PRNG defect or implementation error) then the key will be weaker than expected but the assumption is the key will have n bits of entropy.
ECC has a bit strength equal to half the key length (o... |
###Bits of entropy###
The assumption for all cryptographic operations is that a random key of n bits has n bits of entropy. If it doesn't (due to PRNG defect or implementation error) then the key will be weaker than expected but the underlying assumption of all cryptographic primitives is that an n bit key has n bits... |
I want to do a very simple thing: Given two vectors, I want to encrypt them and do some calculation, then decrypt the result and get the inner product between both vectors. I want to do this as fast as possible for the biggest vector dimension possible.
Can you recommend any reference which may help me understand t... |
A FAQ for an open source project [makes the claim](https://electrum.orain.org/wiki/Frequently_Asked_Questions#How_secure_is_the_seed.3F):
>Indeed, an elliptic curve key of length n provides $n/2$ bits of security.
I have two questions:
1. What is the practical difference between *"bits of entropy"* and *"bits ... |
###Bits of entropy###
The assumption for all cryptographic operations is that a random key of n bits has n bits of entropy. If it doesn't (due to PRNG defect or implementation error) then the key will be weaker than expected but the underlying assumption of all cryptographic primitives is that an n bit key has n bits... |
###Bits of entropy###
The assumption for all cryptographic operations is that a random key of n bits has n bits of entropy. If it doesn't (due to PRNG defect or implementation error) then the key will be weaker than expected but the underlying assumption of all cryptographic primitives is that an n bit key has n bits... |
How to implement following problem in java code for addition? (here I use Paillier homomrphic encryption):
**Input would be to generate a new AES key, encrypt the private data with that key, encrypt the AES key with the FHE key, and send the FHE-encrypted AES key along with the AES encrypted data to the compute node.*... |
How can I implement following problem in java code for addition? (here I use Paillier homomrphic encryption):
**Input would be to generate a new AES key, encrypt the private data with that key, encrypt the AES key with the FHE key, and send the FHE-encrypted AES key along with the AES encrypted data to the compute nod... |
Reading J-PAKE Authenticated Key Exchange Without PKI document :
[J-PAKE][1]
Round 1 : Alice sends out g^x1 and knowledge proof for x1, e.g :
To prove the knowledge of the exponent for X = g^x1
My question is : Is then the recipient (the verifier) of g^x1 + NIZK of x1
able to get the **x1 val... |
Reading J-PAKE Authenticated Key Exchange Without PKI document :
[J-PAKE][1]
> Round 1 : Alice sends out g^x1 and knowledge proof for x1, e.g :
> To prove the knowledge of the exponent for X = g^x1
My question is : Is then the recipient (the verifier) of g^x1 + NIZK of x1
able to get the... |
I am currently learning, and I'm stuck on something that I thought is very simple. On many academic sources they suggest using Extended Euclidean Algorithm to calculate the multiplicative inverse for calculation of the S-Box, but I could not find a proper explanation how to do that. Every practical approach calculates ... |
I am currently learning, and I'm stuck on something that I thought is very simple. On many academic sources they suggest using Extended Euclidean Algorithm to calculate the multiplicative inverse for calculation of the S-Box, but I could not find a proper explanation how to do that. Every practical approach calculates ... |
Is it possible to modify a homomorphic encryption scheme so that it can be CCA2 secure?
From the definition of a homomorphic scheme, it seems that it is malleable, which would result in lack of CCA2 security. So, if we use the regular method to convert a CPA secure scheme to CCA2 secure scheme (using a hash of the me... |
> why we are allowed to replace PRF with random function in security proof?
That's just how security proofs for these kinds of Feistel schemes work - you say something about the cipher when the round function is a truly random function, then you argue that because a PRF is indistinguishable from a random function fo... |
I have a question about security of FE1(Page 16-18) in paper ["format preserving encryption"](https://eprint.iacr.org/2009/251.pdf). Can anyone explain me, why we are allowed to replace PRF with random function in security proof? And also, why is game $G_0$ is the same as game $SPI_1$ (explained in page 6) and game $G... |
I have a question about security of FE1(Page 16-18) in paper ["format preserving encryption"](https://eprint.iacr.org/2009/251.pdf). Can anyone explain me, why we are allowed to replace PRF with random function in security proof? And also, why is game $G_0$ the same as game $SPI_1$ (explained in page 6) and is game $G... |
I have confusion on Feistel word in key size.
Means, "what is the meaning of key size with different feistel word ?"
What does m=2,3,4 represent?
Where m represent different size of feistel word or
we can say 'm' is keywords defined in paper on SIMON and Speck titled "THE SIMON AND SPECK FAMILIES OF LIGHTWEIGH... |
I'm new to this space and find myself stumbling over come cryptographic/mathematical notation. Search engines are not very helpful when copying and pasting Greek letters. Is there any reference that can at least give me names of what I am looking for? |
Where can I find names for cryptographic notation I don't recognize? |
The four Public-key cryptosystems: RSA, ElGamel, DH, and Rabin (all with others) all require some group operations in an integer field or multiplication group of some residue classes. When it comes to encrypting blocks of bits in binary how are these public key cryptosystems performed ? Are byte blocks just converted... |
Given a field $\mathbb{F}_{2^n}$, are there any choices of primitive element $g$ that make the discrete logarithm easier for that generator? That is, are there any degenerate cases?
For example, if I choose a small generator like $g = x$ in $\mathbb{F}_{2^{256}}$, can I quickly find $n$ such that $g^n = a$ for a giv... |
taken the following cryptosystem by DeFeo, Jao and Plut:
https://eprint.iacr.org/2011/506.pdf
The public parameters are defined as:
1. a supersingular curve ***E***
2. bases ***P, Q*** generating the torsion subgroup ***E[l]*** respectively for Alice and Bob
The parameters for the key exchange generated by... |
I'm adding some Diffie-Hellman groups to a program as specified in [RFC 3526, More Modular Exponential (MODP) Diffie-Hellman groups for Internet Key Exchange (IKE)][1].
When I test some of the group parameters per OpenSSL's `DH_check`, a result is returned that essentially states: 2 is not a suitable generator for G... |
Please clarify the below doubt regarding EC point addition and multiplication:
P-Generator Point; a and b are integers; X and Y are EC points.
1) X = (a*P) + (b*P)
2) Y = (a+b)*P
Qestion-1) Are Points X and Y are equal/same?
2) is X 1 scalar point multiplication (i.e. 0.5 + 0.5)
and i... |
Please clarify the below doubt regarding EC point addition and multiplication:
P-Generator Point; a and b are integers; X and Y are EC points.
1) X = (a*P) + (b*P)
2) Y = (a+b)*P
Qestion-1) Are Points X and Y are equal?
2) is X takes 1 scalar point multiplication (i.e. 0.5 + 0.5)
and ... |
Please clarify the below doubt regarding EC point addition and multiplication:
$P$-Generator Point; $a$ and $b$ are integers; $X$ and $Y$ are EC points, defined as follows:
1. $X = (a*P) + (b*P)$
2. $Y = (a+b)*P$
**Questions:**
1. Are the points $X$ and $Y$ equal?
2. Does computing $X$ take 1 scalar p... |
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