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Is there any known instance of a Two Key TDES ever being successfully attacked (in real life), when the key is used to encrypt less than $2^{20}$ words? |
**Background:**
I'm making a program for fun as a learning exercise. I want to generate some *actual random* key material (not pseudorandom) from a JavaScript program. For my program is just for encrypting/decrypting plain text letter by letter so I've chosen to use the [ASCII printable character set][1] (what chara... |
i'm new in cryptography and try to read some articles in this field.
many of this articles talk about non-linear SBOXes, and nothing more on what they mean by their non-linearity.
I have a simple question which i think will guide me through my problem:
- why **'XOR'** operation is Linear but **'ordinary addin... |
why xor is linear operation but ordinary adding is not linear? |
I'm new in cryptography and try to read some articles in this field.
Many of these articles talk about non-linear S-boxes, and nothing more on what they mean by their non-linearity.
I have a simple question which I think will guide me through my problem:
- why is the XOR operation is linear, but ordinary addin... |
> What is the definition of linearity?
Linearity is defined for maps between [vector spaces](https://en.wikipedia.org/wiki/Vector_space#Definition). If you have a field $F$ and two vector spaces $U$ and $V$ over the field $F$, a map $$T:U\rightarrow V$$ is said to be linear if $$T(\gamma_1\odot u_1\oplus\gamma_2\odo... |
The GQ identification scheme is essentially a zero-knowledge proof of a value $x$ such that $x^\mu \equiv J \pmod N$ where $N$ is an RSA modulus and $(\mu,N)$ are system parameters and $J$ is known to the verifier and $x$ only known to the prover.
Now your question is not directly concerned with the aforementioned p... |
I'm making a C++ back end for an application that'll heavily rely on AES-256 and DH. Should I trust third party libraries, or spend (lots of) time to learn about cryptographic implementation and write my own? Is there any reliable authority that can audit the security of a library (like Crypto++ in this case)? I hope t... |
> What is the definition of linearity?
Linearity is defined for maps between [vector spaces](https://en.wikipedia.org/wiki/Vector_space#Definition). If you have a field $F$ and two vector spaces $U$ and $V$ over the field $F$, a map $$T:U\rightarrow V$$ is said to be linear if $$T(\gamma_1\odot u_1\oplus\gamma_2\odo... |
The risks are much higher that there will be mistakes in a novice (or even advanced) implementation. Look at the history of OpenSSL. It was long thought secure, until someone discovered a timing side channel attack. How would you know your code is secure against all the vulnerabilities you don't know about? |
[Context][1]
Assume I wanted to use RSA as the basis for a hash function or DRBG. Also assume that my construct would be insecure if someone were to have the private key. Is there any way generate the a usable public key to be used such that it is provably just as hard for me to generate the private key as it would ... |
Can an RSA public key be generate without ever knowing the factors? |
While a different solution to the problem, key thresholding might be relevant:
http://eprints.qut.edu.au/1054/
http://en.wikipedia.org/wiki/Threshold_cryptosystem
What are you trying to do? |
While a different solution to the problem, key thresholding might be relevant:
http://eprints.qut.edu.au/1054/
http://en.wikipedia.org/wiki/Threshold_cryptosystem
What are you trying to do? |
On pg. 1249 Figure 1 of [this paper][1] it shows m committees are elected in step 1 and then later in step 3 are each given a secret share. But I was wondering if it is possible to pull out the election of m committees from the preprocessing phase and do it in a different phase (like online phase) ? The problem with t... |
how do you distribute secret shares without knowing who to first distribute them to? |
Context: http://blog.cryptographyengineering.com/2013/12/a-few-more-notes-on-nsa-random-number.html
Assume I wanted to use RSA as the basis for a hash function or DRBG. Also assume that my construct would be insecure if someone were to have the private key. Is there any way generate the a usable public key to be use... |
Figure 1 on page 1249 of the “[Multiparty Computation Secure Against
Continual Memory Leakage][1]” paper shows $m$ committees are elected in step 1 and then later in step 3 are each given a secret share.
But I was wondering if it is possible to pull out the election of $m$ committees from the pre-processing phase... |
How do you distribute secret shares without knowing who to first distribute them to? |
Context: http://blog.cryptographyengineering.com/2013/12/a-few-more-notes-on-nsa-random-number.html
Assume I wanted to use RSA as the basis for a hash function or DRBG. Also assume that my construct would be insecure if someone were to have the private key. Is there any way generate the a usable public key to be use... |
Can an RSA public key be generated without ever knowing the factors? |
RSA exhibits symmetrical properties — is it possible to form a cryptanalytic attack? |
Does there currently exist a free online service that accepts a file, hashes it, takes an authoritatively chosen timestamp (from one or more time services), signs these and sends this signed message back? E.g. a *digital notary*, but only with regards to the timestamp and not the validity of the content as legal notari... |
I am trying to prove that:
*"If the gap Diffie-Hellman problem is easy, then the Cha-Cheon signature scheme will be broken."*
Can you help me to prove it? Is there any proof to the relation between the gap Diffie-Hellman problem and the the Cha-Cheon signature scheme?
<sub>My related question: [Can you help m... |
Can hash trees provide quantum resistant signatures to replace RSA for signing securely? What is the key size and how many times can we use same key? |
To give a little background I'm currently implementing a crypto library in JavaScript. *(For any of you out there who also are programmers, do not give me the lecture of "Cryptography" in Javascript/Browsers is a waste of time. A good CSPRNG has other uses than just Cryptography)*
I have started porting across Linux... |
To give a little background I'm currently implementing a crypto library in JavaScript.
I have started porting across Linux's random number generator because its both publicly scrutinized, it is open-source, and is extremely well documented. After browsing around other implementations before settling on Linux's RNG, ... |
If I communicated to a web site that use SSL ,my browser will generate a private key . would the browser store that key in the hard disk ??? or it would just store It in the RAM ?? |
where is my private key stored when I communicate to a website that use SSL? |
> What is the definition of linearity?
Linearity is defined for maps between [vector spaces](https://en.wikipedia.org/wiki/Vector_space#Definition). If you have a field $F$ and two vector spaces $U$ and $V$ over the field $F$, a map $$T:U\rightarrow V$$ is said to be linear if $$T(\gamma_1\odot u_1\oplus\gamma_2\odo... |
This term I have many cryptography courses treating finite fields.
I was wondering if there is any good software that could help doing basic operations in galois fields etc.
I already googled but found nothing appropriate.
What I would need:
A tool/software that can calculate in arbitrary galois fields `gf(p^n)`
... |
For a 10-digits numeric domain (swedish social security numbers), is there a hash function with the following properties?
* no two numbers result in the same hash
* it is not possible to deduce the number from the hash without using brute force.
Also, can I prevent rainbow tables or is the idea of creating an an... |
In this [presentation at the 30c3][1] (long but extremely interesting and well-documented), Jacob Appelbaum spells this advice (circa [43'30"][2]):
> look for the constants that you might find in RC6
I'm trying to make sense out of that; my problem is, there are very few constants that I could find in the [descri... |
What could "look for the constants that you might find in RC6" mean? |
In this [presentation at the 30c3][1] (long but extremely interesting and well-documented), Jacob Appelbaum gave this verbal advice (circa [43'30"][2]):
> look for the constants that you might find in RC6
I'm trying to make sense out of that; my problem is, there are very few constants that I could find in the [d... |
If I communicate with a website that uses encryption (SSL/TLS), my browser will generate a private key. Would the browser store that key on the hard disk or would store just it on the RAM? |
Where is my private key stored when I communicate to a website that uses encryption (SSL/TLS)? |
If I communicate with a website that uses SSL/TLS, my browser will generate a private key. Would the browser store that key on the hard disk or would store just it in the RAM? |
Where is my private key stored when I communicate to a website that uses SSL/TLS? |
Hi I am a little new to security, but in researching digital certificates it seems the only format people describe is x.509. Are there other formats? If so what are they and where can I find information on them? |
Are there other digital certs other than x.509? |
One of the simplest possible cipher modes is setting each successive key as a function `F` of the previous one.
K[0] = Master key
C[i] = E(K[i],P[i]), K[i]=F(K[i-1])
This is similar to the counter mode CTR, buy the key is incremented instead of the plaintext.
Obviously this mode is slower than the oth... |
One of the simplest possible cipher modes is setting each successive key as a function `F` of the previous one.
K[0] = Master key
C[i] = E(K[i],P[i]), K[i]=F(K[i-1])
This is similar to the counter mode CTR, but the key is incremented instead of the plaintext.
Obviously this mode is slower than the oth... |
I'm new to cryptography. I'm trying to learn about sponge function for creating hash functions and generic attacks on it.
l'm looking for the collision finding attack scenario which leads to O(min(2^(n/2) , 2^(c/2)) time complexity which
n is the sponge output length(hash output length)
c is... |
Why is the sponge construction generic collision finding attack has O( min(2^(n/2) , 2^(c/2)) ) complexity? |
When it comes to designing new PKI-based key-exchange protocols, **why are security proofs needed**?
Without them, can we show a protocol's security? Does there exist a PKI-based key-exchange protocol that is secure without a security proof? |
Why do PKI schemes need security proofs? |
Do there exist proofs of security for primitives like hash functions (based on a block cipher) in the PRP model.
I often see proofs in the random oracle model (for hash function based on compression function) and proofs in the ideal cipher model (for hash function based on block cipher).
Are there proofs of such... |
I have question about how a user's identity is verified by a Certification Authority.
As I understand it, the process works as follows:
1. User generates his private key and (with the help of private key) generates his public key.
2. Now user want to register his public key. For this, he has to send the public... |
I'm new to cryptography. I'm trying to learn about sponge function for creating hash functions and generic attacks on it.
l'm looking for the collision finding attack scenario which leads to O(min(2^(-n/2) , 2^(-c/2)) time complexity which
n is the sponge output length(hash output length)
c ... |
Why is the sponge construction generic collision finding attack has O( min(2^(-n/2) , 2^(-c/2)) ) complexity? |
I'm new to cryptography. I'm trying to learn about sponge function for creating hash functions and generic attacks on it.
I'm looking for the collision finding attack scenario which leads to $O(min(2^{(-n/2)} , 2^{(-c/2)})$ time complexity, where $n$ is the sponge output length(hash output length) and $c$ is the ca... |
Why has the sponge construction's generic collision finding attack a complexity of O(min(2^(-n/2) , 2^(-c/2)))? |
Although x.509 is the standard for PKIs with CAs, different certificate formats have been defined for the other 2 major PKI approaches:
- SPKI has defined its [own certificate
format](http://world.std.com/~cme/spki.txt) , still (forever?) in
draft status.
- Web-of-Trust models usually use the OpenPGP cert... |
Why there is a lot of duplicate file finder application using MD5 Algorithm? What is the strength of MD5 in terms of searching duplicate files in hard disk or flash driver or any other storage device? |
Why there is a lot of duplicate file finder application are using MD5 Algorithm? What is the strength of MD5 in terms of searching duplicate files in hard disk or flash driver or any other storage device? |
MD5 is ok here as usual cryptographic attacks do not apply in this scenario.
For details read more.
------
MD5 is currently considered too weak to work as a cryptographic hash. However, for all traditional (i.e. non-cryptographic) hash uses MD5 is often perfectly fine.
MD5 has one important benefit above SHA1... |
MD5 is ok here as usual cryptographic attacks do not apply in this scenario.
The probability of accidental MD5 collision is much less than usual probability for soft error. For details read more.
------
MD5 is currently considered too weak to work as a cryptographic hash. However, for all traditional (i.e. non-c... |
MD5 is ok here as usual cryptographic attacks do not apply in this scenario.
The probability of accidental MD5 collision is much less than usual probability for soft error. For details read more.
------
MD5 is currently considered too weak to work as a cryptographic hash. However, for all traditional (i.e. non-c... |
> Just as a preface, I'm not implementing an HMAC - I just want to understand it as it is part of of my Comp Sci course.
When using Hash-based message authentication codes, I understand that you need to protect the front and back of the MAC to prevent an adversary from modifying the HMAC while in transit.
```HMAC... |
How does the secret key in an HMAC prevent modification of the HMAC? |
Just as a preface: I'm not implementing a HMAC - I just want to understand it, as it is part of of my *Computer Science* course.
When using Hash-based message authentication codes, I understand that you need to protect the front and back of the MAC to prevent an adversary from modifying the HMAC while in transit.
... |
Several [certificate authorities](https://en.wikipedia.org/wiki/Certificate_Authority) operate [RFC-3161](https://tools.ietf.org/html/rfc3161)-compliant time-stamp servers that can be used free-of-charge. [OpenSSL](https://en.wikipedia.org/wiki/OpenSSL) can create RFC 3161 time-stamp requests and verify the responses.
... |
I have read Clifford Cocks ["A Note on 'Non-secret Encryption'"][1] and thought I would try to implement this, but I don't seem to be able to get it to work. I'm obviously missing something.
From the paper:
>a. The receiver picks 2 primes $P$, $Q$ satisfying the conditions:
>>i. $P$ does not divide $Q-1$.
>... |
How does Clifford Cocks 'Non-Secret Encryption' work? |
How can I solve congruence modulo N? |
I have a file of my own that I have encrypted using Coder-Abi. Now, I can just remember part of this password. So, would it be possible (much easier) for me to crack it knowing only part of it? I can remember around 20 of them. The files are pictures, excel and word files.
If there's any software (mainly freeware), ... |
I have read Clifford Cocks "[A Note on 'Non-secret Encryption'][1]" and thought I would try to implement this, but I don't seem to be able to get it to work. I'm obviously missing something.
From the paper:
> 1. The receiver picks 2 primes $P$, $Q$ satisfying the conditions:
> i. $P$ does not divide $Q-1$.
... |
I've studied that the Bleichenbacher's CCA attack on PKCS#1 v1.5. is a base to many versions of attacks in the area.
I'm trying to understand that attack, but every explanation I saw starts with the technical details, without giving some overview, so it's hard to follow...
Can you explain it in a simple words bef... |
Can you explain Bleichenbacher's CCA attack on PKCS#1 v1.5? |
How we can measure key space in transposition algorithms? Should we specify the method, like rail fence? |
Quoting Rivest et al:
> There are 2 natural approaches to implementing timed-release crypto:
> - Use "time-lock puzzles" - computational problems that can not be solved without running a computer continuously for at least a certain amount of time.
- Use trusted agents who promise not to reveal certain informatio... |
> Is the logic for how the enigma machine worked documented somewhere?
Yes!
If you're really interested in *"diving in deeper"* (pun intented), I would like to advise you to check out:
- *"The Cryptographic Mathematics of Enigma"*
Dr. A. Ray Miller
NSA. Center for Cryptologic History. USA. 1996. 3rd... |
In a description of **IND-CPA** (indistinguishability under the chosen plaintext attack), I have been reading the following, simple test:
> The adversary can generate as many messages as he wants. Then, he chooses two messages $m0$ and $m1$, those messages are encrypted, and one of the ciphertexts is sent back to hi... |
with the software exeinfo i identify a function of crypt called "ICE". What is this? How to reverse engineering this function? It is possible to do analogy, having plain text and cipher text? |
A has a message that he wants to send to B, without third side that will be able to know what is the original message.
A encrypts the message and sends it to a server.
The server decrypts the message somehow, and sends it to B.
This way, no one would know what was the original sender, because the server will send ... |
Using `exeinfo`, I have identified a function of `crypt` called `ICE`.
**What is it? How can I find out the workings of the function?**
Some idea's I had for doing this were:
- Perhaps there is a reference
- Could one reverse engineer it?
- If I have examples of (plaintext-ciphertext) pairs, could I const... |
In my **Android** application, it's required to store the **activation status** of the software and keep track of the activation expire date. **What is the best way to store this information?**
Is it safe to store these information in the SQLite database? Otherwise, is it safe to use another way such as store these ... |
$A$ has a message that he wants to send to $B$, without a third party being able to learn the contents of the original message.
$A$ encrypts the message and sends it to a server. The server decrypts the message somehow, and sends it to $B$. This way, no one would know what was the original sender, because the server... |
How can A pass a message to B, while preventing a third party from sniffing infos? |
I know how to calculate the entropy of a key that relates to its selection process. For example if the key space is $1000$, entropy of a randomly chosen key is $1000$. Suppose now you have two keys $X$ and $Y$. The finale key $Z$ is a concatenation of $X$ and $Y$. There are two ways to combine. One is to use XOR and ot... |
When you are using a named curve like P-256 in openSSL, is there any standard key size for ECDH private key keys?
If you look at the `ec_key.c` file in the openSSL source this is what you see:
BN_rand_range(priv_key, order)
Here a cryptographically strong random number is generated which is smaller than t... |
In Wikipedia's article on [Blind signature][1], in the section *Dangers of blind signing* which describes *RSA blinding attack* one reads the following
> This attack works because in this blind signature scheme the signer
> signs the message directly. By contrast, in an unblinded signature
> scheme the signer woul... |
Usability of padding scheme in blinded RSA signature? |
$ed\equiv 1 (mod \phi(n))$
Where does the $\phi(n)$ part come from? How did the inventors of RSA arrive at $\phi(n)$? |
Where does this part of RSA come from? |
> Where does the $\phi(n)$ part come from?
Well, the actual requirement is that, if $n = pq$ and both $p$ and $q$ are prime, we have:
$de \equiv 1 \mod p-1$
$de \equiv 1 \mod q-1$
The first ensures that RSA encryption, followed by RSA decryption, will obtain the original value modulo $p$.
The second ensu... |
$e d \equiv 1 \pmod{\phi(n)}$
Where does the $\phi(n)$ part come from? How did the inventors of RSA arrive at $\phi(n)$? |
$e d \equiv 1 \pmod{\varphi(n)}$
Where does the $\varphi(n)$ part come from? How did the inventors of RSA arrive at $\varphi(n)$? |
For my understanding salts in password hashes are used to prevent the precompuation of plaintext -> hashvalues (rainbow tables).
I know from different threads, it is not necessary to be secret, but nevertheless I was wondering if it would be a problem by making it public?
The background of this question is the fo... |
Can a salt for a password hash be public? |
For my understanding salts in password hashes are used to prevent the precompuation of plaintext -> hashvalues (rainbow tables).
I know from different threads, it is not necessary to keep the salt secret (e.g. encrypt it), but nevertheless I was wondering if it would be a problem by making it public?
The backgrou... |
For my understanding salts in password hashes are used to prevent the precompuation of plaintext$\to$hashvalues (rainbow tables).
I know from different threads, it is not necessary to keep the salt secret (ie it doesn't need to be encrypted), but nevertheless I was wondering if it would be a problem by making it pub... |
A quick web search for "randcam" showed me this german page [Zufallszahlen aus der Webcam][1] ("random numbers from the web cam"). (All other hits on the first Google result page are about an unrelated [Pistonless rotary engine][2]).
This page is about a program available from the same site, which tries to gather en... |
I find myself wanting to test out a practical implementation of a proof-of-retrievability scheme, simply out of curiosity. These schemes seem to be divided into two variations, publicly-verified and privately-verified. Here's a brief explanation of the problem:
Private:
>Alice sends a very large file to Bob.
>... |
Does there exist a proof-of-retrievability scheme that is both simple to implement and publicly-verifiable? |
I find myself wanting to test out a practical implementation of a proof-of-retrievability scheme, simply out of curiosity. These schemes seem to be divided into two variations, publicly-verified and privately-verified. Here's a brief explanation of the problem:
Private:
>Alice sends a very large file to Bob.
>... |
Does there exist a proof-of-retrievability scheme that is publicly-verifiable, limited-use, and does not use homomorphic encryption? |
I am trying to implement Keccak in Java for my school work. And I am getting stuck in two places.
1. On the [summary page](http://keccak.noekeon.org/specs_summary.html) the padding is shown as
> P = M || 0x01 || 0x00 || … || 0x00
>
> P = P xor (0x00 || … || 0x00 || 0x80)
However on the [specification page](ht... |
I'm writing a high school math paper on RSA and I'm wondering if it's possible to relate calculus to RSA. Is calculus used for any part of RSA? It can be for proving equations/theorems, for generating keys, for cracking RSA, etc.
|
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