instruction stringlengths 15 30k |
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Alice has a secret `S` and publishes some public information `P`, about `S` which is insufficient to recreate `S`.
Is there a way that Bob can use `P`, and an arbitrary integer `I` to create an (EC?) public key for which Alice can subsequently calculate the private key, given `I`?
Does this requirement already ... |
Alice has a secret `S` and publishes some public information `P`, about `S` which is insufficient to recreate `S`.
Is there a way that Bob can use `P`, and an arbitrary integer `I` to create an (EC?) public key for which Alice can subsequently calculate the private key, given `I`?
Does this requirement already ... |
Alice has a secret `S` and publishes some public information `P`, about `S` which is insufficient to recreate `S`.
Is there a way that Bob can use `P`, and an arbitrary integer `I` to create an (EC?) public key for which Alice can subsequently calculate the private key, given `I`?
Does this requirement already ... |
Is it safe to use the Sakai–Kasahara key encryption algorithm (SAKKE) for signing, rather than for encryption?
https://en.wikipedia.org/wiki/Sakai%E2%80%93Kasahara_scheme
https://bitbucket.org/a30151/mikey-sakke/src/41da530f6f300ef76878660d4fe6c89010f1c8d6/Java/MSLibrary/src/mikeysakke/crypto/Sakke.java?at=master... |
Is it safe to use the Sakai–Kasahara key encryption algorithm (SAKKE) for signing, rather than for encryption? |
Is it safe to use the Sakai–Kasahara key encryption algorithm (SAKKE) for signing/verification, rather than for encryption?
https://en.wikipedia.org/wiki/Sakai%E2%80%93Kasahara_scheme
https://bitbucket.org/a30151/mikey-sakke/src/41da530f6f300ef76878660d4fe6c89010f1c8d6/Java/MSLibrary/src/mikeysakke/crypto/Sakke.j... |
Is it safe to use the Sakai–Kasahara key encryption algorithm (SAKKE) for signing/verification, rather than for encryption? |
Can we make subtraction result of cipher texts encrypted by Pascal Paillier absolute. Just like we use method **Math.abs()** in Java ?
For example, if we subtract 0 from **1: 1-0 = 1**, it is positive but **0-1 = -1**. My requirement is that this subtraction should always be positive like:
1 - 0 = 1
... |
If I have N bytes of plaintext, does signing it with my private key prove (to holders of my public key) that I have signed that *exact* plaintext messages?
i.e. could an attacker use the plaintext and signature to generate another plaintext which would also verify?
Or do I need to hash the plaintext to provide me... |
Is signing a plaintext sufficient? |
How many plaintext-ciphertext pairs would be needed to guess with probability, say $p=0.5$, the key $k$ of AES under ECB mode?
Most of the articles that I found tried attacks on single plaintext-ciphertext pair. How would the chances on attack on key increase with increase in number of plaintext-ciphertext pairs.
... |
What make them better than OTP using a CSPRNG initialized
with a secret key?
|
Why are there so many stream ciphers out there and even ongoing research? |
Is it safe to use the Sakai–Kasahara key encryption algorithm ([SAKKE](https://en.wikipedia.org/wiki/Sakai%E2%80%93Kasahara_scheme)) for signing/verification, rather than for encryption? ([Example at bitbucket.org](https://bitbucket.org/a30151/mikey-sakke/src/41da530f6f300ef76878660d4fe6c89010f1c8d6/Java/MSLibrary/src/... |
Is it safe to use SAKKE for signing/verification, rather than for encryption? |
Yes, no.
----------
> Does it needs to be new for every transmitted message?
Yes, always, otherwise this qualifies as IV reuse, the keystream produced by the stream cipher is the same (since keystream is independent of plaintext) and you end up with the familiar $M_0 \oplus M_1$.
I think you answered your... |
I have memorized a very long and secure passphrase, that when hashed with sha256, I can use the result as an ECDSA private key, and use it as a brain-address for Bitcoin.
Now I need more bitcoin addresses, and instead of memorizing a new long and secure passphrase, I am thinking about just hashing the previous has... |
Is it safe to generate ECDSA keys from the hash of the previous, over and over again? |
As otus suggests in the comments, it's better to first calculate the frequency of each letter in the decrypted message, and then compare the frequency distribution to what would be expected for English text.
For the comparison, you can use [chi-squared ($\chi^2$) testing](https://en.wikipedia.org/wiki/Chi-squared_te... |
As otus suggests in the comments, it's better to first calculate the frequency of each letter in the decrypted message, and then compare the frequency distribution to what would be expected for English text.
For the comparison, you can use [chi-squared ($\chi^2$) testing](https://en.wikipedia.org/wiki/Chi-squared_te... |
When operating a block cipher in CTR or GCM mode, should the function used to increment the counter or initialization vector be near-constant time? Here, I'm wondering about the "addition with carry" that often occurs. For example:
void IncrementCounterByOne(byte *inout, unsigned int size)
{
for (int ... |
Should Increment functions be near-constant time? |
When operating a block cipher in CTR or GCM mode, should the function used to increment the counter or initialization vector be near-constant time? Here, I'm wondering about the "addition with carry" that often occurs. For example:
void IncrementCounterByOne(byte *inout, unsigned int size)
{
for (int ... |
When operating a block cipher in CTR or GCM mode, should the function used to increment the counter or initialization vector be near-constant time? Here, I'm wondering about the "addition with carry" that often occurs. For example:
void IncrementCounterByOne(byte *inout, unsigned int size)
{
for (int ... |
As otus suggests in the comments, it's better to first calculate the frequency of each letter in the decrypted message, and then compare the frequency distribution to what would be expected for English text.
For the comparison, you can use [chi-squared ($\chi^2$) testing](https://en.wikipedia.org/wiki/Chi-squared_te... |
We know that if n and phi is known, then it is possible to find p and q (initial prime numbers). I have following questions:
1. Assume public key e is not know, How difficult would it be to guess the public key using n, phi, p and q?
2. Assuming we have C1, C1 = M^e mod n is it possible to find out M ?
3. From my... |
Using a CSPRNG to generate a pad *is* a stream cipher. However, that does not mean your question is without merit: if we could kill two birds with one stone by just designing CSPRNGs, that seems like a good idea. So why design dedicated stream ciphers?
One reason is performance. The performance we require from encry... |
We know that if n and phi is known, then it is possible to find p and q (initial prime numbers). I have following questions:
1. Assume public key e is not know, How difficult would it be to guess the public key using n, phi, p and q?
2. Assuming we have C1, C1 = M^e mod n is it possible to find out M without knowing... |
I usually generate a key pair using openssl or Bouncy Castle.
The 256bit private keys *look* fairly random.
Do all values of "private key" have a corresponding public key?
If so, can the public key be found for all arbitrary 256bit values, when treated as if they were public keys?
If not, is there a way to ... |
Are all possible EC private keys valid? |
Dual-ec-drbg is short for Dual Elliptic Curve Deterministic Random Bit Generator; a pseudorandom number generator based on the elliptic curve discrete logarithm problem.
It was standardized in [NIST SP 800-90A](http://csrc.nist.gov/publications/nistpubs/800-90A/SP800-90A.pdf), but Dual_EC has a pretty negative image... |
I usually generate a key pair using openssl or Bouncy Castle.
I'm using curve `secp256k1`.
The 256bit private keys *look* fairly random.
Do all values of "private key" have a corresponding public key?
If so, can the public key be found for all arbitrary 256bit values, when treated as if they were private ke... |
I would like to compress data before encrypting and storing it in a MySQL DB to reduce especially bandwith requirements (compression reduces bandwith by 70-80%). At present, all is handled by a server-based script. In the future, the DB may also be accessible via a web interface.
Various comments on the insecurity ... |
After asking: https://crypto.stackexchange.com/questions/30269/are-all-possible-ec-private-keys-valid I learned that all 32 byte (256 bit) values greater than 0 and less than n are valid private keys. This means that 99% of all 256 bit values are valid private keys. (This was a revelation to me.)
The public key sp... |
Is there a 1:1 mapping between private and public EC keys? |
Points on secp256k1 fulfill the equation:
$$ y^2=x^3+7 \pmod p$$
Your 257 bit compressed point consists of the sign* of $y$ and the value of $x$. You probably want to restrict $x$ to $0 \leq x < p$ as a canonical representation.
Since $y^2$ is obviously a [square](https://en.wikipedia.org/wiki/Quadratic_residu... |
After asking: https://crypto.stackexchange.com/questions/30269/are-all-possible-ec-private-keys-valid I learned that all 32 byte (256 bit) values greater than 0 and less than n are valid private keys. This means that 99% of all 256 bit values are valid private keys. (This was a revelation to me.)
The public key sp... |
After asking: https://crypto.stackexchange.com/questions/30269/are-all-possible-ec-private-keys-valid I learned that all 32 byte (256 bit) values greater than 0 and less than n are all valid private keys. This means that 99% of all 256 bit values are valid private keys. (This was a revelation to me.)
The public ke... |
After asking: https://crypto.stackexchange.com/questions/30269/are-all-possible-ec-private-keys-valid I learned that all 32 byte (256 bit) values greater than 0 and less than n are all valid private keys. This means that 99% of all 256 bit values are valid private keys. (This was a revelation to me.)
The public ke... |
Is it possible and safe to use SAKKE for signing/verification, rather than for encryption? |
I am working on an embedded device which send/receive data and stored them in ciphertext mode (encrypted mode ). Now what's best approach for storing Keys (I used ARM CORTEX M series MCU) ?
1-Storing keys in the SRAM memory,in each booting sequence ,inject keys to the embedded MCU and store them in the SRAM memory... |
I am working on an embedded device which send/receive data and stored them in ciphertext mode (encrypted mode ). Now what's best approach for storing Keys (I used ARM CORTEX M series MCU) ?
1. Storing keys in the SRAM memory,in each booting sequence ,inject keys to the embedded MCU and store them in the SRAM memory.... |
Using a text book example, Alice and Bob want to communicate securely using encrypted messages over an insecure channel (the Internet). Alice and Bob have decided to use ECDH (using ephemeral keys generated per session) and start off by each generating a public/private key pair using Curve P-256 - using SHA1PRNG for ... |
Using a text book example, Alice and Bob want to communicate securely using encrypted messages over an insecure channel (the Internet). Alice and Bob have decided to use ECDH (using ephemeral keys generated per session) and start off by each generating a public/private key pair using Curve P-256 - using SHA1PRNG for ... |
Is it wise to use HOTP (raw bytes) as a key for HMAC data signatures? |
We know that if $n$ and $\phi$ is known, then it is possible to find $p$ and $q$ (initial prime numbers). I have following the questions:
1. Assume the public key $e$ is not known, how difficult would it be to guess the public key using $n$, $\phi$, $p$ and $q$?
2. Assuming we have $c_1$, $c_1 = m^e \bmod n$ is ... |
> Assume the public key $e$ is not known, how difficult would it be to
> guess the public key using $n$, $\phi$, $p$ and $q$?
$e$ can be chosen completely arbitrary and independently of the modulus and related variables ($\phi,p,q$). You can't learn anything about $e$ (assuming $d$ isn't given) only with the modulu... |
Looking at [this question](http://crypto.stackexchange.com/questions/12823/ecdsa-vs-ecies-vs-ecdh) it appears that you can either have a tool that can derive keys or bits or can be used to sign and verify something, is there an EC way to do both with the same keypair? |
Looking at the question [“ECDSA vs ECIES vs ECDH”](http://crypto.stackexchange.com/questions/12823/ecdsa-vs-ecies-vs-ecdh) it appears that you can either have a tool that can derive keys or bits, or can be used to sign and verify something. Is there an EC way to do both with the same keypair? |
Currently learning and reading about the fascinating SSL Key Exchange and came upon the Apple GOTOFAIL incident back in 2014. I'm going through the code during that time and came across this section.
err = sslRawVerify(ctx,
ctx->peerPubKey,
dataToSign, ... |
Let's say that you have some small number of RSA signatures of known data: you know some pairs $(m_k, c_k)$ such that ${c_k}^e \equiv m_k \mod n$. If you know $e$, because probably it's one of $\{3, 17, 65537\}$, is it possible to recover $n$? |
Is it possible to recover an RSA modulus from its signatures? |
I noticed that with only an RSA public key, it is possible/tractable to calculate $m^{p+q} \mod n$ for any $m$ without knowing $p$ or $q$. Namely, $m^{p+q} \equiv m^{n+1} \mod n$. (This follows from $\phi(n) = n - p - q + 1$ and the order of all multiplicative subgroups $\mod n$ dividing $\phi(n)$.)
Is this useful... |
Instead of rolling your own, you should use an established password hash, like [PBKDF2][1], scrypt or maybe bcrypt, they try to be more expensive on GPUs and custom cracking hardware. (Argon2 [is also an option][2], but not widely supported yet.)
> (this will take about a million times longer compared to the usual m... |
Instead of rolling your own, you should use an established password hash, like [PBKDF2][1], scrypt or maybe bcrypt, they try to be more expensive on GPUs and custom cracking hardware. (Argon2 [is also an option][2], but not widely supported yet.)
> (this will take about a million times longer compared to the usual m... |
Alice and Bob engage to compute a secure function `f(a,b)` where `a` and `b` must be present in a set `U`. Although both Alice and Bob know `f(a,b)`, how can Alice confirm that `b` is present in `U` and Bob confirm that `a` is present in `U`? |
Is it wise to use HOTP (raw bytes) as a key for HMAC? |
Let's say that you have some small number of RSA signatures of known data: you know some pairs $(m_k, c_k)$ such that ${c_k}^e \equiv m_k \pmod n$. If you know $e$, because probably it's one of $\{3, 17, 65537\}$, is it possible to recover $n$? |
I have some bytes, and I (ECDSA) sign them with my private key.
The resultant (71) bytes are the signature.
What is the name of the bytes I have signed?
(If this was encryption, they would be called the plaintext.) |
What's the correct name for bytes which are to be signed? |
In protocols/systems which use ECDSA, is it common for the message to contain the public key of the message signer?
If not, how do recipients know that the message has been signed by the *correct* private key, and how do they know which public key to use to verify the signature? |
Is it usual for a signed message to contain the public key of the signer? |
Typically, a message will contain some sort of identifying information of the sender, such as the `From` header of an e-mail. In any case, if the sender of the message is unknown, what's the point of using signatures at all? The purpose of a signature is to ascertain that the message was written and sent by its purport... |
You are probably aware of the existence of public key certificates. A certificate proves the authenticity of a public key, basically by signing the value of that public key (plus some data on the owner of that key) with a private key of some third party. This third party often is a central Certificate Authority (CA) th... |
I have some bytes, and I sign them with my private key using ECDSA. The resultant (71) bytes are the signature.
But what is the name of the bytes I have signed? (If this were encryption, they’ld be called “plaintext”.) |
> I assume the recommended approach is to use a KDF function like HKDF, but what is the security implication of taking an SHA-256 hash and using it directly for AES-256 or truncating it for AES-128 (Alice and Bob are using Java which doesn't have a native implementation of HKDF and I don't think it is a good idea to tr... |
I try to compare the performances (cost of Enc, Dec, ... size of keys, ciphertexts, ...) of IBE schemes using lattices (LWE hardness assumption) or pairing (Diffie-Hellman hardness assumption).
I've observed that performances of lattice based schemes are often expressed in terms of $n$ (the dimension of the lattice)... |
Are you simply wanting Alice to sign her message to Bob? <br><br>
Carol could decrypt Bobs message, check the plaintext hash against Alices signature, and prove it came from Alice.
|
> I assume the recommended approach is to use a KDF function like HKDF, but what is the security implication of taking an SHA-256 hash and using it directly for AES-256 or truncating it for AES-128 (Alice and Bob are using Java which doesn't have a native implementation of HKDF and I don't think it is a good idea to tr... |
I am newbie in visual cryptography..
I just read paper Visual Cryptography by Moni Naor and Adi Shamir. And I'm stuck on chapter k out of n construction. I know, on page 8, there is already step by step how to construct it.
But I still do not understand.. especially at function h (number 1), how to get that func... |
Is there a way hide a message inside another text using a criptography cypher/algorithm, preserving the sense of the other text, and without anybody noticing the hidden message?
I mean something that can be processed manually or by a computer (ie. I don't mean to hide a message like "Attack X" saying "I went to X on... |
> I assume the recommended approach is to use a KDF function like HKDF, but what is the security implication of taking an SHA-256 hash and using it directly for AES-256 or truncating it for AES-128 (Alice and Bob are using Java which doesn't have a native implementation of HKDF and I don't think it is a good idea to tr... |
I'm wondering what's the standard (or canonical) notation for "a message along with its signature", i.e.
$$
Message~||~\sigma_k\{Message\}
$$
Here the duplicated $Message$ is tedious. Is there a way to put it more elegantly? |
Is there a way hide a message inside another text using a cryptographic cipher/algorithm, while preserving the sense of the other text and without anybody noticing the hidden message?
I mean something that can be processed manually or by a computer. More specific: I don't mean to hide a message like `“Attack X”` say... |
Is there a way to hide a text message $A$ inside another text $B$ using a cryptographic cipher/algorithm, while preserving the sense/meaning of $B$ and without anybody being able to notice there is a message $A$ hidden in text $B$?
I am looking for something that can be processed either manually or by a computer.
... |
Is there an algorithm to hide text in another tex, while preserving the meaning of the later? |
I am newb to visual cryptography. I’ve just read the paper “Visual Cryptography” by Moni Naor and Adi Shamir and I'm stuck on the chapter about the “$k$ out of $n$” construction. I am aware that, on page 8, there is a step-by-step explanaton on how to construct it… but I still do not understand how it works.
Specif... |
I'm wondering what's the standard (or canonical) notation for "a message along with its signature", i.e.
$$
\mathit{Message}~\Vert~\sigma_k(\mathit{Message})
\text.
$$
Here the duplicated $\mathit{Message}$ is tedious. Is there a way to put it more elegantly? |
Is there a standard notation for a message concatenated with its signature? |
I am new to visual cryptography. I’ve just read the paper [“Visual Cryptography” by Moni Naor and Adi Shamir](http://www.wisdom.weizmann.ac.il/mathusers/naor/PAPERS/vis.pdf) and I'm stuck on the chapter about the “$k$ out of $n$” construction. I am aware that, on page 8, there is a step-by-step explanation on how to co... |
I'm starting to study about visual cryptography, but I am stuck with the following problem.
On paper ["Visual Cryptography" by Moni Naor and Adi Shamir](http://www.wisdom.weizmann.ac.il/mathusers/naor/PAPERS/vis.pdf), on page 6. How to read/what is the meaning of
$$J^0_i = 0^{i-1}10^{k-i}$$
and
$$J^0_k = 1^... |
Is it possible to correct the exponent of an RSA public key if it has been altered ? If so how |
Is it possible to change the exponent of an RSA public key? |
Is it possible to correct the exponent of an RSA public key if it has been altered? |
Imagine Alice is applying for a new job. Alice an idea of the minimum salary that she is willing to accept—let's call this value `A`. Bob, the hiring manager for a company that Alice is applying to, also has a number in mind: the maximum acceptable salary that he is be willing to pay to fill the position—let's call thi... |
Why is just one challenge-response phase sufficient for IND-CPA security? |
Why is only one oracle + challenge-response phase sufficient for IND-CPA security? |
I'm looking for a concrete algorithm to generate one time passwords. The situation is as follows:
Alice and Bob exchanged a passphrase over a secure channel in the beginning. They want to symetrically encrypt data in the future, and every consecutive enryption/decryption process should use a one-time password.
Fo... |
Which method to generate one time password? |
Imagine Alice is applying for a new job. Alice has an idea of the minimum salary that she is willing to accept—let's call this value `A`. Bob, the hiring manager for a company that Alice is applying to, also has a number in mind: the maximum acceptable salary that he is willing to pay to fill the position—let's call th... |
Is there an algorithm to hide text in another text, while preserving the meaning of the later? |
i read a lot about Diffie-Hellmann, but there is one thing i dont understand: why does the modulos p need to be a prime? What if it would not be a prime?
|
Why does the modulos of Diffie Hellmann needs to be a prime? |
With ECDSA is there a way for the verifier to prove any properties of K, without knowing K or the private key Da?
(I understand that K should be random, or follow RFC6979, but I'm curious.)
In particular, could the verifier prove that:
1. K is odd
2. K has some mathematical relation to one of the curve parame... |
With ECDSA is there a way for the verifier to prove any properties of K? |
With ECDSA is there a way for the verifier to prove any properties of k, without knowing k or the private key Da?
(I understand that k should be random, or follow RFC6979, but I'm curious.)
In particular, could the verifier prove that:
1. k is odd
2. k has some mathematical relation to one of the curve parame... |
With ECDSA is there a way for the verifier to prove any properties of k? |
With ECDSA is there a way for the verifier to prove any properties of k, without knowing k or the private key Da?
(I understand that k should be random, or follow RFC6979, but I'm curious.)
In particular, could the verifier prove, given a signature (r,s) and a message m, that:
1. k is odd
2. k has some mathem... |
With ECDSA is there a way for the verifier to prove any properties of $k$, without knowing $k$ or the private key $D_A$?
(I understand that $k$ should be random, or follow RFC6979, but I'm curious.)
In particular, could the verifier prove, given a signature $(r,s)$ and a message $m$, that:
1. $k$ is odd
2. $k... |
With ECDSA is there a way for the verifier to prove any properties of $k$? |
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