instruction stringlengths 15 30k |
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Are there open source implementations of SSE and OPE?
Can anyone please point to sample codes, if available.
Edit: If cryptDB is not an option, what other options are available?
(Indeed, these schemes are weak that is why cryptDB proposes onion layers for encryptions) |
Are there open source implementations of SSE and OPE?
Can anyone please point to sample codes, if available.
**EDIT**
If cryptDB is not an option, what other options are available?
(Indeed, these schemes are weak — which is why cryptDB proposes onion layers for encryption.) |
Assumptions:
- Alice and Bob use (cryptographically secure, hardware-rng generated) 4096 bit keys.
- Each message is encrypted using a new key; meaning: once a key is used, it's destroyed.
- Alice and Bob only need to encrypt/decrypt messages up to a length of 256 bytes.
Since the 4096 bit keys practically repr... |
Having 4096 bit keys and short (< 256 byte) messages, can I simply use the key as OTP? |
Assumptions:
- Alice and Bob use (cryptographically secure, hardware-rng generated) 4096 bit keys.
- Each message is encrypted using a new key; meaning: once a key is used, it's destroyed.
- Alice and Bob only need to encrypt/decrypt messages up to a length of 256 bytes.
- To keep it simple, key-exchange is not p... |
**Preamble:**
There is currently a zoo of various logics for evaluating (proving) security in cryptographic protocols. The idea is that, by expressing these protocols using some logic, you can create a formula describing some property (such as shared secrecy, message authentication, and perfect forward secrecy).
... |
OTP is (theoretically) perfect encryption algorithm.
Let's assume that these problems are solved:
- Fast generation of independent and identically distributed random variables
- Perfect key distribution system
- Key only used once.
- Key destroyed after use, without side channels that would allow any non-tru... |
So I have a file that is XY **Exabytes** big. I create a sha512 hash from it.
**Q**: Are there any theoretical chances that I can retrieve the original data just from the sha512 hash?
p.s: or are there any better hashes then sha512? |
Would it be possible to generate the original data from a sha512 checksum? |
Brainwallet is a program that takes a passphrase (hopefully a good one) and deterministically creates a Bitcoin wallet. This wallet can be used for transactions, then deleted from the computer. To get access to the wallet again, one only needs the passphrase to recreate it.
Does something similar exist for GPG?
I... |
The answer depends on what the XY Exabytes big data contains. If it contains very small amount of information, it may be possible for attacker to find the correct input by a trial. Maybe the XY exabytes of data is just some large 8K resolution video.
In case the XY Exabytes big data contains significant amount of i... |
OTP is (theoretically) perfect encryption algorithm.
Let's assume that these problems are solved:
- Fast generation of independent and identically distributed random variables
- Perfect key distribution system
- Key only used once.
- Key destroyed after use, without side channels that would allow any non-tru... |
The answer depends on what the XY Exabytes big data contains. If it contains very small amount of information, it may be possible for attacker to find the correct input by a trial. Maybe the XY exabytes of data is just some large 8K resolution video available from specific http://xxx.xx.xxx address or just full of zero... |
No, because a hash behaves (simply put) like a lossy compression function.
Meaning: you can use a hash like a sort of checksum, which enables you to identify and compare data. Using hashes, you can see if data has been modified (which, if re-hashed, would show a different hash as a result), or if two or more data ... |
So, I have a file that is XY ***Exabytes*** big. I create a SHA-512 hash from it.
Are there any theoretical chances that I can retrieve the original data just from the sha512 hash?
Also, are there any better hashes then sha512? |
Would it be possible to generate the original data from a SHA-512 checksum? |
I have a file that is encrypted in AES using a 16 char string. The string is `(a-zA-Z0-9)` and `.,?!`. Also, it only contains words from a dictionary (but they can be lower/upper case). What would be the most effective way to brute force this?
(No, I'm not trying to brute force passwords. Who would store passwords i... |
What would be the most effective way to brute force a 16 char AES key? |
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 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 me ... |
Is there proof to the relation between the gap Diffie-Hellman problem and the the Cha-Cheon signature scheme? |
I am attempting to encrypty/decrypt a long message in RSA using javascript (with crypto-js and jsbn libraries).
I posted this on stackoverflow too but I figured someone here on crypto might be able to help as well.
so far, to encrypty/decrypt short messages I have the following code:
$$ function encrypt(signed... |
From what I read from [here](http://en.wikipedia.org/wiki/Elliptic_Curve_DSA#Security), it says the **deterministic** generation of k can help prevent certain type of attacks (Such as the one happened to Sony). However, my question is that, wouldn't the deterministic property be predictable as compared with [probabili... |
I am attempting to encrypty/decrypt a long message in RSA using javascript (with crypto-js and jsbn libraries).
I posted this on stackoverflow too but I figured someone here on crypto might be able to help as well.
so far, to encrypt/decrypt short messages I have the following code:
function encrypt(signed... |
How one would go about design something like Google Drive/Dropbox providing the following features:
1. files are _encrypted_ and _decrypted_ on the client
2. files can be synced between devices
3. the service provider shouldn't be store private keys/passwords on servers
4. if the user can have only one password t... |
How one would go about design something like Google Drive/Dropbox providing the following features:
1. files are _encrypted_ and _decrypted_ on the client
2. files can be synced between devices
3. the service provider shouldn't be store private keys/passwords on servers
4. if the user can have only one password t... |
Where can I find Secp256k1 ECDSA test vectors? |
I am using RSA to encrypt some data but I would like to eliminate the possibility of message replay. By message replay I mean sending a valid message multiple times to the original recipient. It is obvious that an attacker can capture a valid message without knowing its contents and replaying it.
Is there any effici... |
How can I prevent a message replay with RSA? |
Are there any Secp256k1 ECDSA test examples available? |
Is there an effective way for public key generation in homomorphic encryption schemes? |
Suppose both I and my friend have a set of integer numbers. We want to know the number of common elements in our two sets but without knowing elements of the sets of each other. So I don't want my friend to know any element of my set and he don't want me to know his. But we want to know how many elements are in the int... |
Is there an algorithm to find the number of intersections of two sets? |
How can I generate a one-time password? |
Is there a way to provide proof of batch RSA security? |
I was studying Crypto, and this question came up. Using a PRG like the multiplicative congruence generator :
bi+1 = a . bi mod m;
How do I prove that the output of this PRG, or any PRG's whatsoever is easily distinguished from a random sequence of numbers?
Thanks in advance. |
How do I prove that this PRNG is easily distinguished from a random sequence of numbers (modulo m)? |
How can I calculate the SHA-256 "midstate"? |
Suppose that you see all IP communication packets between two computers for a day, as they pass through a connecting router, and this amounts to 10MB. You additionally know that all data transmission follows the standard "RSA-1024 plus AES-128" protocol. To be even more specific, suppose you know only one computer is d... |
Can you distinguish encryption methods from the output? |
Text book question of Chapter 9 of "Crypto and Network Security" by William Stallings:
When using the RSA Algorithm — if a small number of repeated encodings give back the plain text, what is the likely cause this happens?
|
What is the likely cause the RSA algorithm gives back plain text in this case? |
One of our users seems to have been hit bb [CryptoLocker][1]. As a result, he has a hard drive full of encrypted files. The ransomware claims to have used public key encryption on the files.
If we know exact contents of what some of the files were *prior* to being encrypted, would it be feasible to use those files ... |
Find private key if some of message is known? |
In [proxy re-encryption][1] schemes, a proxy is given special information that allows it
to translate a ciphertext under one key into a ciphertext of the same message under a
different key.
How practical is PRE? Is it possible for achieving PRE for AES?
[1]: http://en.wikipedia.org/wiki/Proxy_re-encryptio... |
How practical is proxy re-encryption for AES? |
Most of the current key exchange techniques are based on public-key cryptography. Are there any key exchange/establishment techniques based on symmetric-key cryptography too?
In my setup primary assumption is both communicating parties can have pre-shared key and further they need to exchange messages to derive a l... |
Is there a symmetric-key cryptography based on key establishment techniques? |
As it is well known that QKD systems are prone to simple MITM attacks… what authentication techniques are being used in QKD to prevent those attacks in practice? |
What authentication techniques can be used by QKD Systems? |
Are there any papers, books, or link where it explains how the plain vanilla "textbook RSA" is actually implemented in practice with all the padding and stuff?
Basically, I would like to know the intricacies of implementing an algorithm into production level code… |
Are there any papers explaining how to port textbook RSA to realworld RSA? |
The classic multiparty computation protocols are defined around " Untrusted parties trying to compute something together".
But is there a cryptographic abstraction for, "Trusted parties trying to compute together in presence of untrusted server"?
Basically, I am looking for something like multi-player homomorph... |
What kind of multiparty computation is this? |
[Homomorphic encryption schemes][1] are PKE schemes with an additional special method *Evaluate*.
The *Evaluate* method takes input any function (as boolean circuit) and encrypted inputs of the function and evaluates the circuit. The results of such function are still encrypted under the public key $PK$.
Now, if... |
Can we proxy-re-encrypt using homomorphic encryption schemes? |
I've played a lot with VIC and enjoy its complexity and effectiveness as a field cipher. However, RC4 has caught my attention lately and I've read there is a RC4-52 variant that can be done by hand.
Can anybody describe the rc4-52 algorithm? Is it with a deck of cards and just a swap of the values, or must they stil... |
Can you help me understand how RC4-52 is done using pen-and-paper? |
What's the state of the attack to get the first pre-image on MD4?
Is it still $2^{102}$ as described by
Gaëtan Leurent in ["MD4 is Not One-Way" ](http://www.di.ens.fr/~leurent/files/MD4_FSE08.pdf)? |
What's the state of the attack to get the first pre-image on MD4? |
Suppose you have 2 drives you want to encrypt using different encryption algorithms, as an example: AES256 and Twofish.
I am aware that using the same password for both could potentially weaken either one or both because it would build a relationship.
But AFAIK it's only true if both passwords are hashed into the... |
Well, this is essentially homework (it wasn't assigned, however you are attempting to learn from it), and so I won't give you an explicit answer; instead, I'll try to point you in a direction where you can figure out the answer yourself.
First of all, how would you solve this if you were given the values $a$ and $m$... |
I recently read this article, and I would love it someone explained this in more detail:
http://android-developers.blogspot.co.uk/2013/02/using-cryptography-to-store-credentials.html
What is happening:
Up until Android 4.1, android used a SecureRandom provider, that, given the same seed, after using setSeed(se... |
I've recently been reading an article about "[using cryptography to store credentials](http://android-developers.blogspot.co.uk/2013/02/using-cryptography-to-store-credentials.html)", and I would love it someone explained this in more detail…
Up until Android 4.1, Android used a SecureRandom provider, that, given th... |
Why is sharing the seed and using SecureRandom "deterministically" so bad? |
Suppose you have 2 drives you want to encrypt using different encryption algorithms, as an example: AES256 and Twofish.
I am aware that using the same password for both could potentially weaken either one or both because it would build a relationship.
But AFAIK it's only true if both passwords are hashed into the... |
I was studying Crypto, and this question came up. Using a PRG like the multiplicative congruence generator :
bi+1 = a . bi mod m;
How do I prove that the output of this PRG, or any PRG's whatsoever is easily distinguished from a random sequence of numbers? |
Both determinism and non-determinism are useful. The question is which one you use for which purpose.
Determinism is generally useful for expanding a short secret to a long one. For example, you may keep a short random secret and use it to generate a long keystream that you can XOR against messages for encryption an... |
From what I read in Wikipedia's article "[Elliptic Curve DSA ~ Security](http://en.wikipedia.org/wiki/Elliptic_Curve_DSA#Security)", the *"deterministic"* generation of $k$ can help prevent certain type of attacks (such as the one happened to Sony).
However, wouldn't the deterministic property be predictable as com... |
Isn't the deterministic property of (EC)DSA a security problem? |
Both determinism and non-determinism are useful. The question is which one you use for which purpose.
Determinism is generally useful for expanding a short secret to a long one. For example, you may keep a short random secret and use it to generate a long keystream that you can XOR against messages for encryption an... |
One of our users seems to have been hit by [CryptoLocker][1]. As a result, he has a hard drive full of encrypted files. The ransom-ware claims to have used public key encryption on the files.
If we know exact contents of some of the files *prior* to them being encrypted, would it be feasible to use those files to d... |
Knowing pre-encryption data, can we find the private key CryptoLocker used? |
I'd like to create a database of questions and answers so that an attacker with access to the database can't obtain either the questions or the answers.
If H0 and H1 are secure hashes, looking up the answer to a question might proceed as follows:
lookup(H0(question)) -> value
H1(question) XOR value -> answer
... |
Can you get two unpredictable hashes from the same message with, e.g. SHA1? |
I am reading bicycle cryptanalysis of the full AES paper. What do they mean by *"sharing active S-boxes"*? How can this concept can be advantageous to make a bicycle? If there is someone who reads this paper, please explain it to me. |
Can you explain what the AES paper means by "sharing active S-boxes"? |
One-Time Padding is (theoretically) perfect encryption algorithm. Let's assume that these problems are solved:
- Fast generation of independent and identically distributed random variables
- Perfect key distribution system
- Key only used once.
- Key destroyed after use, without side channels that would allow... |
Is there a companion algorithm for OTP to ensure integrity and/or authentication? |
I'm trying to decrypt a message that is encrypted using a LUC encryption scheme and running into roadblocks. I know that with RSA if Alice and Bob use the same public modulus but different encryption exponents, with $\gcd(n_A,n_B)=1$ then you can find the plaintext $M$.
I'm provided $R$ (public modulus), $n_A$ (Ali... |
Can you help me understand the Common Modulus Attack in a Lucas Group? |
I'd like to create a database of questions and answers so that an attacker with access to the database can't obtain either the questions or the answers.
If `H0` and `H1` are secure hashes, looking up the answer to a question might proceed as follows:
lookup(H0(question)) -> value
H1(question) XOR value -... |
I have recently begun studying crypto. If it's one thing I have learned it's that we should not implement our own crypto. Therefore we should look to using existing software and libraries.
1) When I go to implement something that needs data security, there are many options -- openssl, mcrypt, truecrypt, crypt, pycry... |
Which crypto libraries/programs do we have the most confidence in? |
Can keys from Bitcoin's Hierarchical Deterministic Wallets be correlated? (reducing privacy?) |
I'm curious what would happen in the following scenario:
Suppose an alien gets a hold of a cipher-text of sufficiently large length. And suppose he has the means to verify a successful decryption.
But the alien has no clue what cipher is used and assumes it's unbreakable with anything but brute-force whatever it is... |
Hypothetical unknown cipher - security in obscurity? |
I'm curious what would happen in the following scenario:
Suppose an alien gets a hold of a cipher-text of sufficiently large length. And suppose he has the means to verify a successful decryption.
But the alien has no clue what cipher is used and assumes it's unbreakable with anything but brute-force whatever it is... |
I have recently begun studying crypto. If it's one thing I have learned it's that we should not implement our own crypto. Therefore we should look to using existing software and libraries.
1. a) When I go to implement something that needs data security, there are many options -- openssl, mcrypt, truecrypt, crypt, py... |
Can keys from Bitcoin's Hierarchical Deterministic Wallets be correlated (reducing privacy)? |
I'm curious what would happen in the following scenario:
Suppose an alien gets a hold of a cipher-text of sufficiently large length. And suppose he has the means to verify a successful decryption.
But the alien has no clue what cipher is used and assumes it's unbreakable with anything but brute-force whatever it is... |
Given $R$, a prime $p$ and two bases $g_1$ and $g_2$, is it possible to decide if $R = g_1^r$ mod $p$ or $R = g_2^r$ mod $p$ without knowing $r$? |
Is it possible to decide the base of a discrete logarithm? |
I was studying Crypto, and this question came up. Using a PRG like the multiplicative congruence generator:
$b_{i+1} = a \cdot b_i \mod m$
How do I prove that the output of this PRG, or any PRG's whatsoever is easily distinguished from a random sequence of numbers? |
One-Time Padding is (theoretically) perfect encryption algorithm. Let's assume that these problems are solved:
- Fast generation of independent and identically distributed random variables
- Perfect key distribution system
- Key only used once.
- Key destroyed after use, without side channels that would allow... |
I'm curious what would happen in the following scenario:
Suppose an attacker gets a hold of a cipher-text of sufficiently large length. And suppose he has the means to verify a successful decryption.
But the attacker has no clue what cipher is used and assumes it's unbreakable with anything but brute-force whatever... |
Plenty of ciphers come out of the USA from government research or selection competitions. AES and DES are examples.
Are there any public ciphers produced by other states, China or Iran for example? |
I would like to know: What is the relationship between an **attack** and an **attack model**.
For example, let $\Pi$ be the Lamport signature scheme. This signature has it's security based on the one-way function. The Grover algorithm (an **attack**) inverts this function with complexity $\mathrm{O}(2^{n/3})$. Furt... |
Plenty of ciphers come out of the USA from government research or selection competitions. AES and DES are examples.
Are there any public ciphers produced by other states, China or Iran for example? Do you really think they trust AES? |
I'm curious what would happen in the following scenario:
Suppose an attacker gets a hold of a cipher-text of sufficiently large length. And suppose he has the means to verify a successful decryption.
But the attacker has no clue what cipher is used and assumes it's unbreakable with anything but brute-force whatever... |
Both determinism and non-determinism are useful. The question is which one you use for which purpose.
Determinism is generally useful for expanding a short secret to a long one. For example, you may keep a short random secret and use it to generate a long keystream that you can XOR against messages for encryption an... |
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