instruction stringlengths 15 30k |
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I'm not completely clueless as to what it means, but I'd like to understand it at a higher level.
The highest encryption type used by Active Directory domain controllers for Kerberos authentication traffic is AES256-CTS-HMAC-SHA1-96.
The first part, AES256-CTS: That's AES with a 256-bit symmetric key operating in... |
What does AES256-CTS-HMAC-SHA1-96 mean in relation to Kerberos? |
I'm not completely clueless as to what it means, but I'd like to understand it at a higher level.
The highest encryption type used by Active Directory domain controllers for Kerberos authentication traffic is AES256-CTS-HMAC-SHA1-96.
The first part: AES256-CTS. That's AES with a 256-bit symmetric key operating in... |
Is there any way to generate values only between 0 and 255 with Diffie-Hellman method? I need to create keys to communication algorithms with 32 and 16 numbers between that range.
The idea is to exchange the keys between the participants using the results of the Diffie-Hellman key agreement algorithm. Then we create... |
How can I construct a distinguisher given an inverter? |
"Now, who promises that $|Enc(m)|$ depends on $|m|$?" $\:$ the protocol designers
"Isn't it possible that $|Enc(m_0)| = |Enc(m_1)|$?"
<br>
It is perfectly possible that $\:\:\big|\hspace{-0.03 in}\operatorname{Enc}(m_{\hspace{.02 in}0})\big| \:=\: \big|\hspace{-0.03 in}\operatorname{Enc}(m_1)\big|\;\;$.
<br><br... |
It's well-known that Shor's algorithm can solve integer factorization, discrete logarithm and discrete log over elliptic curves in cubic time. This implies that cryptosystems like RSA, ElGamal, and Elliptic Curve Diffie-Hellman (ECDH) are vulnerable to quantum computers.
Are there any existing public-key cryptosyst... |
I'm reading [this paper][1] and here say:
> With an ACR hash function $F$ the key $K$ is announced and the adversary wins if she manages to any collision $M,M'$ for $f = F_K$. The points $M$ and $M'$ may depend arbitrarily on $K$.
My question is Could be bring me any example of messages $M$ and $M'$ such that dep... |
I'm reading [this paper][1] and here say
> While it might be easy to find a collision $M,M'$ in $F_K$ by making both
> $M,M'$ depend on $K$ (Any Collision Resistance), the adversary may be unable to find collisions if she
> is forced to commit to one point of the collision before seeing $K$.
> We call this **w... |
I'm reading [the paper][1] and here say
> one practical advantage of $TCR$ (Target Collision Resistant) over $ACR$ (Any Collision Resistan) because $x$ must be specified before $K$ is known, birthday attacks to find collisions are not possible $T$
I understood the definition of notion $TCR$ but My question is Wh... |
I'm reading [this paper][1] and here say
> While it might be easy to find a collision $M,M'$ in $F_K$ by making both
> $M,M'$ depend on $K$ (Any Collision Resistance), the adversary may be unable to find collisions if she
> is forced to commit to one point of the collision before seeing $K$.
> We call this **w... |
Consider GregS's comment to this question (more specific to bouncycastle's provider implementation):
http://stackoverflow.com/questions/11717646/bouncycastle-rsa-key-size-and-padding
> The mode, ECB in this case, is ignored for RSA.Use PKCSPadding. The
> max amount of data you can encrypt is the size of the modu... |
Is it true for Java that the transformation mode and padding is ignored when using RSA? |
These days, the best practice for storing passwords is to use a scheme like scrypt or bcrypt. The goal of these schemes is to make dictionary attack inefficient for an attacker but it also slows down legitimate use of the function.
If you're doing thousands of password checks per second, there is a real world cost ... |
Why don't we use MACs to store passwords? |
I'm reading [this paper][1], which compared TCR (Target Collision Resistant) and ACR (Any collision Resistant). It says
> we wish to stress one important practical advantage of TCR over ACR: because $x$ must be specified before $K$ is known, birthday attacks to find collisions are not possible
I understood the de... |
I'm reading [this paper][1] which states:
> With an ACR hash function $F$ the key $K$ is announced and the adversary wins if she manages to any collision $M,M'$ for $f = F_K$. The points $M$ and $M'$ may depend arbitrarily on $K$.
Could you give me an example of messages $M$ and $M'$, so that they depend arbitrar... |
Is there any way to generate values only between $0$ and $255$ with the Diffie-Hellman method? I need to create keys to communication algorithms with $32$ and $16$ numbers between that range.
The idea is to exchange the keys between the participants using the results of the Diffie-Hellman key agreement algorithm. Th... |
I'm reading the paper “[Collision-Resistant Hashing? Towards Making UOWHFs Practical][1]” which states:
> With an ACR hash function $F$ the key $K$ is announced and the adversary wins if she manages to any collision $M,M'$ for $f = F_K$. The points $M$ and $M'$ may depend arbitrarily on $K$.
Could you give me an ... |
I'm reading the paper “[Collision-Resistant Hashing? Towards Making UOWHFs Practical][1]” which states:
> While it might be easy to find a collision $M,M'$ in $F_K$ by making both
> $M,M'$ depend on $K$ (Any Collision Resistance), the adversary may be unable to find collisions if she
> is forced to commit to one... |
I'm reading the paper “[Collision-Resistant Hashing? Towards Making UOWHFs Practical][1]” , which compared TCR (Target Collision Resistant) and ACR (Any collision Resistant). It says
> we wish to stress one important practical advantage of TCR over ACR: because $x$ must be specified before $K$ is known, birthday att... |
I'm reading the paper “[Collision-Resistant Hashing? Towards Making UOWHFs Practical][1]” which states:
> With an ACR hash function $F$ the key $K$ is announced and the adversary wins if she manages to any collision $M,M'$ for $f = F_K$. The points $M$ and $M'$ may depend arbitrarily on $K$.
Could you give me an ... |
How can two (or more) parties share and agree upon a common random seed? |
Is there any way to generate values only between $0$ and $255$ with the Diffie-Hellman method? I need to create keys for communication algorithms with $32$ and $16$ numbers between that range.
The idea is to exchange the keys between the participants using the results of the Diffie-Hellman key agreement algorithm. T... |
Is there any way to generate values only between $0$ and $255$ with the Diffie-Hellman method? I need to create keys for communication algorithms with $32$ and $16$ numbers between that range.
The idea is to exchange the keys between the participants using the results of the Diffie-Hellman key agreement algorithm. T... |
Can Diffie-Hellman generate values in a specified range? |
I am a hobby programmer with a background in biology and have developed an encryption program based on DNA. I tried to make it hard to crack, but it's essentially a substitution cipher and uses the default Java random number generator so my guess it could be cracked relatively easily. But how do I find out how good my ... |
ECB, CBC and such cipher modes are something that relate to symmetric cryptography.
In context of RSA, it is important to study from documentation of the product what they mean as they do not ordinarily apply.
Based on the articles you provide, this statement is correct:
> The mode, ECB in this case, is ignored ... |
Alice has a message, generates a one time pad, encrypts her message and sends it to Bob. Bob generates his **own** one time pad, encrypts the message again, and sends it back to Alice. Alice then decrypts this message using her one time pad, sends it back to Bob who then decrypts it the last time using his one time pad... |
ECB, CBC and such cipher modes are something that relate to symmetric cryptography.
In context of RSA, it is important to study from documentation of the product what they mean as they do not ordinarily apply.
Based on the articles you provide, this statement is correct:
> The mode, ECB in this case, is ignored ... |
I'm developing my own protocol and I'll use Diffie-Hellman to achieve PFS. It will work in this way:
The symmetric encryption algorithm will be AES_256_CBC.
The DH parameters will be:
P: a 2048-bit safe prime as defined in [RFC 3526][1].
Generator: 2 (also defined in RFC 3526).
Secret Exponent: a 512-bit ephem... |
In a PostgreSQL database, I can see the following fields in a table (for a specific record):
User = administrator
Password = "ceMv9Me6go"
Now the following are true:
- The password length is not fixed, thus I'm leaning towards it being an
encryption rather than a hash.
- The actual password is "password... |
There are many RFC documents giving large primes to use in Diffie-Hellman. However, I couldn't find standards on the $p$ and $q$ large primes used in the DSA signature scheme. This is proving to be a major obstacle in my own toy implementation of DSA, as generating these primes uses much messier math and code than the ... |
Are there public $p$ and $q$ numbers for use in DSA? |
In a PostgreSQL database, I can see the following fields in a table (for a specific record):
User = administrator
Password = "ceMv9Me6go"
Now the following are true:
- The password length is not fixed, thus I'm leaning towards it being an
encryption rather than a hash.
- The actual password is "password... |
"Now, who promises that $|Enc(m)|$ depends on $|m|$?" $\:$ the protocol designers
"Isn't it possible that $|Enc(m_0)| = |Enc(m_1)|$?"
<br>
It is perfectly possible that $\:\:\big|\hspace{-0.03 in}\operatorname{Enc}(m_{\hspace{.02 in}0})\big| \:=\: \big|\hspace{-0.03 in}\operatorname{Enc}(m_1)\big|\;\;$.
<br><br... |
Can anyone give an example where (asymmetric) crypto can go wrong due to selection of wrong groups? |
In the algorithms of certificateless Signature approach of Al-riyami and patersons (http://eprint.iacr.org/2003/126.pdf),
1. Why there is need of **partial private key extract algorithm** ?
2. Why should it needed when calculating **user's private keys by user**.?
3. Whether **partial private key extract algorithm... |
In the algorithms of certificateless Signature approach of Al-riyami and patersons (http://eprint.iacr.org/2003/126.pdf),
1. Why there is need of **partial private key extract algorithm** ?
2. Why should it needed when calculating **user's private keys by user**.?
3. Whether **partial private key extract algorithm... |
Related to the algorithms of [certificate-less Signature approach of Al-Riyami and Patersons](http://eprint.iacr.org/2003/126.pdf)…
1. Why is there a need for a *"partial private key extract algorithm"*?
2. Why should it be needed when calculating *"user's private keys by user"*?
3. Is *"partial private key extra... |
Can you explain partial private key extract algorithm in certificateless Public key cryptography? |
Related to the algorithms of [certificate-less Signature approach of Al-Riyami and Patersons](http://eprint.iacr.org/2003/126.pdf)…
1. Why is there a need for a *"partial private key extract algorithm"*?
2. Why should it be needed when calculating *"user's private keys by user"*?
3. Is *"partial private key extra... |
Related to the algorithms of [certificate-less Signature approach of Al-Riyami and Paterson](http://eprint.iacr.org/2003/126.pdf)…
1. Why is there a need for a *"partial private key extract algorithm"*?
2. Why should it be needed when calculating *"user's private keys by user"*?
3. Is *"partial private key extrac... |
Can two people with different one time pads securely exchange a message like this? |
Suppose I have H(M|K) and that H is not weakly collision resistant. If I have a message mac pair (M,MAC), how is it possible to find another message mac pair (M2,MAC2)? My thinking for this problem is that if the hash isn't weakly collision resistant, then I can find another message M2 such that H(M|K)=H(M2|K) and thus... |
Why is appending the key to a mesage and then hashing that insecure if the hash isn't weakly collision resistant? |
I'm reading [“Collision-Resistant Hashing? Towards Making UOWHFs Practical”][1] and in the Section 2 say:
> Hash functions like MD5 or SHA-1 have no explicit key. But no notion
> of collision-freeness has been offered for such a keyless setting. To
> get a sense why this is so, suppose $f$ is a function $f:\sum^*... |
What is the best way to implement a cascade encryption?
I'm trying to figure out how to cipher a string (or message) using Serpent-Twofish-AES and then store the keys.
I'll provide an explanation, then maybe someone is going to be able to explain how to resolve the issue I'm facing. I've read the TrueCrypt docume... |
How to store keys for a cascading encryption? |
What is the difference between various modes in FPE? |
One potential consideration is that combinations of security principles may have unintended vulnerabilities. This is not to say they you cannot combine such approaches, but most combinations have been well studied and then recommended by trusted 3rd parties (academic or governmental or institutional).
While not in ... |
I have been trying to understand how secret sharing methods like Shamir's secret sharing solve the problem of a share revealing information about the secret. I guess there are some random numbers involved, but how is it done mathematically? |
How does secret sharing solve the partial exposure problem? |
I know that a SHA-1 is a criptographic hash function unkeyed, and too, that in practice SHA-1 is used. But in the theoric all hash function are defined with keys, then my question is How I will be able to formalize a SHA-1 hash function using keys (in other word in theoric)? |
I still got the impression that you did not really have read [my answer to a related question](http://crypto.stackexchange.com/questions/11585/certificateless-cryptography/11586#11586).
But still, I try to briefly answer your questions here. First of all, *private key extraction* essentially means *private key gener... |
I know that a SHA-1 is a criptographic hash function unkeyed, and too, that in practice SHA-1 is used. But in the theoric all hash function are defined with keys, then my question is How I will be able to formalize a SHA-1 hash function using keys (in other word in theoric)? In security proof Which approach could be us... |
Ok, so this is a very possible stupid question, but one of those things that has sat at the back of my mind for a while.
We all know that MD5 has issues, and these have been known for about a decade. So this is theoretical. I'm not considering using it for anything.
Question is this. If MD5 generates a 32 digi... |
What is the best way to implement a cascade encryption?
I'm trying to figure out how to cipher a string (or message) using Serpent-Twofish-AES and then store the keys.
I'll provide an explanation, then maybe someone is going to be able to explain how to resolve the issue I'm facing. I've read the TrueCrypt docume... |
I'm reading [“Collision-Resistant Hashing? Towards Making UOWHFs Practical”][1] and in the Section 2 it says:
> Hash functions like MD5 or SHA-1 have no explicit key. But no notion
> of collision-freeness has been offered for such a keyless setting. To
> get a sense why this is so, suppose $f$ is a function $f:\s... |
I'm reading [“Collision-Resistant Hashing? Towards Making UOWHFs Practical”][1] and in the Section 2 it says:
> Hash functions like MD5 or SHA-1 have no explicit key. But no notion
> of collision-freeness has been offered for such a keyless setting. To
> get a sense why this is so, suppose $f$ is a function $f:\s... |
Imagine I'm signing up for the 99th new web site this month.
I somehow take my secret key (which I have [written down][1] on a card in my wallet) and the domain name of the site and feed them both into some algorithm (perhaps a HMAC?),
and type the resulting hash into the "password" field of the registration form.
... |
Is there a cryptographic hash function that can be performed with pencil and paper? |
What is the ideal system for an encryption scheme? For a pseudorandom permutation the ideal one is a random permutation, for a pseudorandom function the ideal one is a random function. For an encryption scheme do we have a well known application describing an ideal system for an encryption? Maybe the one-time pad? |
Determine the Key given ciphertexts and plaintexts? |
Given two sets of plaintexts and their corresponding ciphertexts, how does one determine the key $K$?
The ciphertexts are:
$$C_1= (P_1 \oplus K_0) || K_1$$ ,
and
$$C_2= (P_2 \oplus K_0) || K_1$$
$K = K_0 || K_1$ (string of bits).
Drive an equation in one unknown (e.g. $K_1$). is it possible to proce... |
Given two sets of plaintexts and their corresponding ciphertexts, how does one determine the key $K$?
The ciphertexts are:
$$C_1= (P_1 \oplus K_0) + K_1$$ ,
and
$$C_2= (P_2 \oplus K_0) + K_1$$
$K = K_0 || K_1$ (string of bits).
Drive an equation in one unknown (e.g. $K_1$). is it possible to proceed... |
Given two sets of plaintexts and their corresponding ciphertexts, how does one determine the key $K$?
The ciphertexts are:
$$C_1= (P_1 \oplus K_0) + K_1$$
and
$$C_2= (P_2 \oplus K_0) + K_1$$
$K = K_0 + K_1$ (string of bits).
where $+$ means addition mod $2^n$.
How do we find the unknowns (eg, $K_... |
Given two sets of plaintexts and their corresponding ciphertexts, how does one determine the key $K$?
The ciphertexts are:
$$C_1= (P_1 \oplus K_0) + K_1$$
and
$$C_2= (P_2 \oplus K_0) + K_1$$
$K = K_0 || K_1$ (string of bits).
where $+$ means addition mod $2^n$.
How do we find the unknowns (eg, $K... |
In a PostgreSQL database, I can see the following fields in a table (for a specific record):
User = administrator
Password = "ceMv9Me6go"
Now the following are true:
- The password length is not fixed, thus I'm leaning towards it being an
encryption rather than a hash.
- The actual password is "password... |
How do I cryptanalyze a password field? |
In a PostgreSQL database, I can see the following fields in a table (for a specific record):
User = administrator
Password = "ceMv9Me6go"
Now the following are true:
- The password length is not fixed, thus I'm leaning towards it being an
encryption rather than a hash.
- The actual password is "password... |
The first thing I would want to know is if the encoding is deterministic. This should be easy to test. Change the password, but make it the same value. If the value in the DB doesn't change, then it is deterministic. Also try this for a few users. Give them all the same password and see if the DB entries are the same. ... |
I have been given a problem in preparation for my cryptography final that I'm not sure how to solve. It asks me to suppose a scenario where instead of where an attacker would intercept some message from Alice (g^a) mod p and (g^b) mod p from bob, and then replacing each of these with g^e, the attacker would replace it ... |
I commonly hear statements along the lines of "all cryptograms are crackable - it's only a matter of time".
Is there a proof to show that any cryptogram is "crackable"? The proof may be of a more philosophical form rather than relying on mathematical proofs. I really don't know what to expect, but would be fascinate... |
Is there a proof for showing any cryptogram is crackable? |
My area of expertise is reverse engineering, specifically embedded systems. I do attack cryptographic systems, but this largely involves key recovery or exploiting the implementation.
I was asked to reverse engineer a simple Windows executable used as part of a challenge-response protocol used for intruder alarm sys... |
If I follow the [wikipedia][1] or [crypto.stackexchange][2] definition, any simple XOR encryption where the key is as long as the plain text should qualify as a secure block cipher.
Now I thought what would happen if I just use this together with a block cipher mode of operation? After all, they should build a secu... |
I am a beginning programmer interested in coding an application of my own to encrypt sensitive files of mine. For example: lists of passwords, bank accounts, Credit Card numbers etc.
I was wondering what would be the easiest encryption algorithms to learn from a purely theoretical point of view? |
At Blackhat 2013 this week, there was a talk saying RSA is (essentially) doomed in the near future.
[networkworld.com ~ “Black Hat: Elliptic curve cryptography coming as smarter algorithms threaten RSA”](http://www.networkworld.com/news/2013/080213-black-hat-elliptical-curve-cryptography-272476.html?page=1)
What ... |
NSA recently released [SIMON and SPECK][1] light weight block ciphers . Although initial spec release did not have much of cryptanalysis details . Two works later appeared providing the cryptanalysis for the same [SIMON][2] and [SPECK][3].
But how to interpret those results ? are they considered good ? or bad ?
F... |
The NSA recently released [SIMON and SPECK][1] light weight block ciphers. Although initial spec release did not have much of cryptanalysis details, two works later appeared providing the cryptanalysis for the same [SIMON][2] and [SPECK][3].
But how should we interpret those results? Are they considered good or bad?... |
How should we interpret the cryptanalysis results of SIMON and SPECK? |
Let's first get something out of the way. You say _".. key-recovery attack for SPECK32/64 .."_. This is not true. The cryptanalysis you linked attacks SPECK32/64 __with 10 rounds__. This is __less than half__ the amount of rounds used for SPECK32/64.
Then onto your actual question, is $2^{29}$ chosen plaintexts a go... |
The NSA recently released [SIMON and SPECK][1] light weight block ciphers. Although initial spec release did not have much of cryptanalysis details, two works later appeared providing the cryptanalysis for the same [SIMON][2] and [SPECK][3].
But how should we interpret those results? Are they considered good or bad?... |
When working with an additive homomorphic encryption scheme (say Pallier's), is there an efficient way to get the *encrypted* value of a comparison test to an integer value (I realise that an unencrypted comparison test would make the encryption scheme worthless)?
I know there are (rather costly in number of rounds... |
When working with an additive homomorphic encryption scheme (say Pallier's), is there an efficient way to get the *encrypted* value of a comparison test to an integer value (I realise that an unencrypted comparison test would make the encryption scheme worthless)?
I know there are (rather costly in number of rounds... |
This is not true: when used correctly the [One Time Pad](http://en.wikipedia.org/wiki/One-time_pad) is [information-theoretic secure](http://en.wikipedia.org/wiki/Information_theoretic_security), which means it can't be broken with cryptanalysis. However, part of being provably secure is that you need as much key mater... |
Even without an OTP increasing key-sizes quickly get to the point where "enough time and resources" is unrealistically large. For example using all the energy emitted by our sun over its whole lifetime only allows decryption with a really small probability. With slightly larger keys even the energy of the whole univers... |
Not all ciphers are can be broken, even by infinitely powerful adversaries.
When used correctly the [One Time Pad (OTP)](http://en.wikipedia.org/wiki/One-time_pad) is [information-theoretic secure](http://en.wikipedia.org/wiki/Information_theoretic_security), which means it can't be broken with cryptanalysis. Howeve... |
To get a public key of some organization or someone we want to send an encrypted message to, we need to make a request to CA asking that organization's public key. CA then returns X509 certificate. It contains CA's signature. To decrypt it we need to have a CA's public key. How can we securely obtain CA's public key? |
How can we get CA's public key? |
How does certificate revocation list (CRL) work? How can I send a request to the CA to add my current private key to the CRL, so no one except me can add my certificate to the CRL? Thanks. |
I've got my private key compromised. How does CRL work? |
To get a public key of some organization or someone we want to send an encrypted message to, we need to make a request to CA asking that organization's public key. CA then returns X509 certificate. It contains CA's signature. To decrypt it we need to have a CA's public key. How can we securely obtain CA's public key?
... |
What happens when a root CA has its private key compromised? Then all children in the tree are compromised too? And then all certificates are compromised? What needs to happen then? |
What happens when a root CA has its private key compromised? |
Even without an OTP increasing key-sizes quickly get to the point where "enough time and resources" is unrealistically large. For example the chance of breaking a 256 bit key with the best conventional computer thermodynamics allows using all the energy emitted by our sun over its whole lifetime still leads to negligib... |
> I commonly hear statements along the lines of "all cryptograms are crackable - it's only a matter of time
Using a perfectly random key which is as long as the message itself,not a pseudo-random key) cannot be broken no matter how fast the attacker's computer is. This is guaranteed by information theory and doesn't... |
> I commonly hear statements along the lines of "all cryptograms are crackable - it's only a matter of time"
Using a perfectly random key which is as long as the message itself, not a pseudo-random key, cannot be broken no matter how fast the attacker's computer is. This scheme is called one-time-pad and its securit... |
What happens when a root CA has its private key compromised? Then all children in the tree are compromised too? And then all certificates are compromised? What needs to happen then?
<sub>Related:
- [How can we get CA's public key?](http://crypto.stackexchange.com/q/11712/6961)
- [I've got my private key compro... |
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