instruction stringlengths 15 30k |
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I'm looking all over the internet for prime192v3's parameters. I think I may have found them [here](http://bouncycastle.sourcearchive.com/documentation/1.32/jdk1_80_2org_2bouncycastle_2asn1_2x9_2X962NamedCurves_8java-source.html), but it doesn't say what variable each number matches to. Is there some central place wher... |
Discrete log problem is hard. Is it also hard to calculate generator $g$ given $g^a, a$? |
OpenSSL block ciphers return length of the text as output of the encryption (`envelope_seal()`), and If I have to send the length over network, I append the length with the ciphertext as I can transmit only one field and `envelope_open()` needs the length of the ciphertext. Is there any other way that I can calculate t... |
A friend mentioned that he used the sine of a number, i.e. sind(54), to generate long passwords. This way he only has to remember sine 54 and have a calculator to get his password back. I am wondering if this is secure. It can easily generate a long password, but because the numbers are not random would it be vulnerabl... |
Are passwords generated from sine vulnerable to certain attacks? |
I'm using Wikipedia and Handbook of Applied Cryptography as references. I know that ESSIV generates an initialization vector (IV) by combining a hashed key with the sector number.
However, I only see an IV in CBC, PCBC, CFB, and OFB modes of operation e.g. chained modes. CTR and ECB are NOT chained modes, so where d... |
How does CTR-ESSIV work ? (cryptsetup Linux) |
I have come up with the following rudimentary example of how ECC relates to asymmetric keys.
Is this a valid explanation of ECC and its relationship to asymmetry?
To only be deciphered by the person with the private key, it is necessary to use methods nontrivial in cryptography. To randomize the key, a set woul... |
are Barreto-Naehrig Curves suitable for pairing-based cryptography? |
Suppose I have a fixed-length ciphertext encrypted with a random AES Key (Kenc) and with an arbitrary ciphermode.
To authenticate such ciphertext, I generate an other random AES Key (Kauth).
Then, I compute the CBC-MAC Tag of the ciphertext with Kauth as the key.
Finally, I store the ciphertext and the associa... |
CBC-MAC: it is secure to mac a fixed length ciphertext with different key? |
CBC-MAC: is it secure to authenticate a fixed length ciphertext? |
Suppose I have a fixed-length arbitrary ciphertext.
To authenticate such ciphertext, I generate a random AES Key (which is defacto different to the Key I use for encryption).
Then, I compute the CBC-MAC Tag of the ciphertext with Kauth as the key.
Finally, I store the ciphertext and the associated Tag in my da... |
Suppose I have a fixed-length arbitrary ciphertext.
To authenticate such ciphertext:
- I generate a random AES Key *Kauth*.
- Then I compute the CBC-MAC Tag of the ciphertext with *Kauth*.
- Finally, I store the ciphertext and the associated Tag in my database.
For decryption process:
- I get... |
Suppose I have a fixed-length arbitrary ciphertext.
**To authenticate such ciphertext:**
- I generate a random AES Key *Kauth*.
- Then I compute the CBC-MAC Tag of the ciphertext with *Kauth*.
- Finally, I store the ciphertext and the associated Tag in my database.
**For decryption process:**
... |
Suppose I have a fixed-length arbitrary ciphertext.
**To authenticate such ciphertext:**
- I generate a random AES Key *Kauth*.
- Then I compute the CBC-MAC Tag of the ciphertext with *Kauth*.
- Finally, I store the ciphertext and the associated Tag in my database.
**For decryption process:**
... |
Suppose I have a fixed-length arbitrary ciphertext.
**To authenticate such ciphertext:**
- I generate a random AES Key *Kauth*.
- Then I compute the CBC-MAC Tag of the ciphertext with *Kauth*.
- Finally, I store the ciphertext and the associated Tag in my database.
**For decryption process:**
... |
The Identity-Based Encryption consist of four randomized algorithms: Setup, Extract, Encrypt, Decryption. the setup phase is done by Public-key generator, encrypt by sender and decryption by receiver. the Extract phase is done by PKG or receiver? |
Identity-Based Encryption consist of four algorithms. Extract phase is one of theme and it is done by PKG or receiver? |
The Identity-Based Encryption consist of four randomized algorithms: Setup, Extract, Encrypt, Decryption. The Setup phase is done by Public-key generator, Encrypt by sender and Decryption by receiver. the Extract phase is done by PKG or receiver? |
Identity-Based Encryption consist of four algorithms. Extract phase is one of them and it is done by PKG or receiver? |
The Identity-Based Encryption consist of four randomized algorithms: Setup, Extract, Encrypt, Decryption. The Setup phase is done by Private-key generator, Encrypt by sender and Decryption by receiver. the Extract phase is done by PKG or receiver? |
I need to implement GCM GHASH in hardware, using FPGA. The data bus is 640 bits, so I will use 5 adder/multiplier blocks in parallel. The message size is fixed and AAD is 0.
A little example: message = 5 x 640 bits.
cycle 1: process 640 bits (add/multiply)
cycle 2: process 640 bits (add/multiply)
cycle 3: proc... |
I need to implement GCM GHASH in hardware, using FPGA. The data bus is 640 bits, so I will use 5 adder/multiplier blocks in parallel. The message size is fixed and AAD is 0.
A little example: message = 5 x 640 bits.
cycle 1: process 640 bits (add/multiply)
cycle 2: process 640 bits (add/multiply)
c... |
OTP requires 1) random key material as long as the message to be encrypted 2) no reuse of the key material or any part, ever 3) secure transmission of the key material between communicants 4) no key material becomes known to anyone ever.
And even then, OTP only guarantees that no other encryption will be harder to bre... |
Are there any key agreement/exchange/establishment protocols which are NOT based around the Diffie-Hellman protocol or handshakes using public key cryptograaphy? DH seems to form the basis of this single class and I'd rather use something different than this stale, old one. |
I want to start using NaCL to sign messages that will go into a message queue, and I noticed that it generates different keys for each operation. Is there a reason for this? Can I not use the same PK for signing and encryption? |
Why does NaCL have different keys for signing and encryption? |
Suppose I have a fixed-length arbitrary ciphertext.
**To authenticate such ciphertext:**
- I generate a random AES Key $K_{auth}$.
- Then I compute the CBC-MAC Tag of the ciphertext with $K_{auth}$.
- Finally, I store the ciphertext and the associated Tag in my database.
**For decryption process:**... |
According to this [paper](https://eprint.iacr.org/2008/356.pdf) entitled *"Using Commutative Encryption to Share a Secret"* they define their modulus to be a large prime p, which is public. Both exponents are private in this case.
According to the wikipedia article on RSA [link](http://en.wikipedia.org/wiki/RSA_(cry... |
Prime modulus for RSA and sharing a secret? |
As you can probably guess, I just watched *The Imitation Game*, which hasn't really gotten points for historical accuracy...
During World War II, Turing and his team fret that they can't know the plaintext of the Enigma messages they intercept. In a Eureka moment, it occurs to Turing to try a message that probably c... |
Is the idea of a known plaintext attack really that new? |
I want to use SHA-512 for hashing in a system that must be FIPS-compliant. When I look at [the FIPS 140 list of approved providers][1], I don't see SHA from any provider as being an approved algorithm, I only see it as an "other" algorithm. [In FIPS 180, SHA-512 is listed as being approved][2], although I don't see any... |
Consider a function $$f: \{0,1\}^n \rightarrow \{0,1\}^{poly(n)} $$
with the following properties:
- hard to invert, i.e. given $f(x)$, hard to find $x$
- hard to find a collision, i.e given $f(x)$, hard to find $x'$, such that $f(x') = f(x)$
- indistinguishable from a random number i.e given $f(x)$ and $y... |
Generic name for (?hash) functions of form $\{0,1\}^n \rightarrow \{0,1\}^{poly(n)}$ |
I need to implement GCM GHASH in hardware, using FPGA. The data bus is 640 bits, so I will use 5 adder/multiplier blocks in parallel. The message size is fixed and AAD is 0.
A little example: message = 5 x 640 bits.
cycle 1: process 640 bits (add/multiply)
cycle 2: process 640 bits (add/multiply)
c... |
I´m kind of new in this so I apologize in advance for any noob mistakes (feel free to point it out)
We are developing a licensing mechanism on our software, and I would like some advice.
The software is installed on premises on the client, good old .Net application. We are planning on using the [Portable.Licens... |
I´m kind of new in this so I apologize in advance for any noob mistakes (feel free to point it out)
We are developing a licensing mechanism on our software, and I would like some advice.
The software is installed on premises on the client, good old .Net application. We are planning on using the [Portable.Licens... |
If key changes itself when it send/receive message what would be could breaking method?
So:
$E: m×k$ in which $k$ is last generated key
$D: c×k$ in which $k$ is last generated key
$k{_n} = k_{n-1}×m$ method using for generating new key, both in decryption and encryption.
Note: $×$ marks any operation or f... |
I presume you are referring to hardcore, one-way functions (OWF's) with polynomial span?
There have been a flurry of publications in the past 12 months relating to these functions and their implied possibility or practicability.
The challenge with hardcore predicates has been in achieving polynomial span...
[Bellar... |
Can we use EED with 2 keys (K1 K1 K3) rather than EDE (k1,k2,k1) ? We measure the strength of DES by the effort (in term of number of tries) in finding some K1 & K2 to match a known plaintext and ciphertext pair . Will EED have the same strength as EDE ? Which one is stronger?
Can anyone please help me in this ? |
3DES Modes EED orEDE? |
> For variable-length messages, there are three different ways to generate the tags.
> 1. $Tag = MAC_k(\Sigma_i m_i)$.
> 2. $t_i = MAC_k(m_i)$ and $Tag = (t_1, ..., t_l)$.
> 3. $t_i = MAC_k(i||m_i)$ where $i$ is a sequence number and $Tag = (t_1, ..., t_l)$.
> Find an attack for each case.
I have been lo... |
> For variable-length messages, there are three different ways to generate the tags.
> 1. $Tag = MAC_k(\Sigma_i m_i)$.
> 2. $t_i = MAC_k(m_i)$ and $Tag = (t_1, ..., t_l)$.
> 3. $t_i = MAC_k(i||m_i)$ where $i$ is a sequence number and $Tag = (t_1, ..., t_l)$.
> Find an attack for each case.
><sub>*Problem... |
Perhaps someone can confirm my intuition:
A tree hash with leaves of size 1 (for example Blake2 in a tree-hash mode) would of course not be very efficient.
But it seems that it might be a suitable way (or maybe the only way?) to provide a verifier that's still useful if the underlying content is subject to inten... |
Can a tree hash with leaf-size of 1 byte support verification of content with elided ranges, at a cost of at most 2 supplied internal-node hashes? |
Simply as stated, with AES running in CTR mode, can somebody work out the key (without brute-forcing) given we know about the plaintext, IV and also the ciphertext.
Assuming we also know about the cipher block size & key length.
In other words, we have the pseudo random AES CTR stream + IV, can we work out what t... |
Is the key deducible with AES CTR when we know about the plaintext, IV and the ciphertext? |
Let $G$ be any group where group operations, as well as finding the inverse of an
element, can be performed quickly, but the discrete log problem is difficult. Consider
the following cryptosystem:
1. Alice chooses an element $g ∈ G$, a message $m ∈ G$, and an integer $k_A$.
2. Alice computes $s = mg^{k_A}$ and ... |
I presume you are referring to hardcore, one-way functions (OWF's) with polynomial span?
There have been a flurry of publications in the past 12 months relating to these functions and their implied possibility or practicability.
The challenge with hardcore predicates has been in achieving polynomial span...
[Bellar... |
Why do we need Encrypt Then Mac? |
I'm wondering if there is any library supporting pseudorandom function, so I can specify the key length and output domain.
Is that write that I need to use a block cipher for this purpose?
Any help with this would be much appreciated. |
I've always seen MACs as a way to provide integrity and authentication. You would just append it to some message in clear.
But this is clearly not the case when you're doing Encrypt Then Mac. When you do that you provide authentication to something that already has authentication (to decrypt we need to know the key)... |
Why not just encrypt the message and the hash of the message to achieve cryptographic integrity? |
I'll take this in parts:
>But this is clearly not the case when you're doing Encrypt Then Mac. When you do that you provide authentication to something that already has authentication (to decrypt we need to know the key).
Encryption, by itself, [does not provide authentication](http://security.stackexchange.com/q... |
I'm wondering if there is any library supporting pseudo-random function, so I can specify the key length and output domain.
Is it correct that I need to use a block cipher for this purpose?
Any help with this would be much appreciated.
|
I'll take this in parts:
>But this is clearly not the case when you're doing Encrypt Then Mac. When you do that you provide authentication to something that already has authentication (to decrypt we need to know the key).
Encryption, by itself, [does not provide authentication](http://security.stackexchange.com/q... |
Can we tell that any shift cipher to be decrypted needs an algorithm of complexity `n * n!` ? |
Can we tell that any shift cipher to be decrypted needs an algorithm of complexity `n * n!` ? (where `n` is number of possible values. 26 in case of English language). |
I am trying to find how much time an AES encryption and decryption takes for a given amount of data and key. In all the cases encryption takes way lesser processing time than decryption. I tried to get this answer somewhere else but can't find. May I know why does decryption takes a lot more time than encryption for AE... |
How on earth did you arrive at that formula?
You can break a Caesar cipher by calculating the result of applying all of the $n-1$ (i.e., 25) possible shifts to the ciphertext and picking the one that makes sense. The computational complexity is just $\mathcal{O}(n)$.
If you want to automate the process based on f... |
Can we tell that any shift cipher to be decrypted needs an algorithm of complexity `n * n!` ? (where `n` is number of possible values. 26 in case of English language).
My idea of reaching n * n! was as follows: Take the word BRAZIL for example
we have 26 possibilities for B, 25 for R, 24 for A... etc thus `O(n!)`
... |
> For variable-length messages, there are three different ways to generate the tags.
> 1. $Tag = MAC_k(\Sigma_i m_i)$.
> 2. $t_i = MAC_k(m_i)$ and $Tag = (t_1, ..., t_l)$.
> 3. $t_i = MAC_k(i||m_i)$ where $i$ is a sequence number and $Tag = (t_1, ..., t_l)$.
> Find an attack for each case.
><sub>*Problem... |
The definition of the Blum Blum Shub cryptographically secure pseudorandom number generator is $x=x^2 \mod N$ where $N=p \times q$, $p \in \mathbb P$, and $q \in \mathbb P$. Supposedly, the security comes from an attacker not knowing the factors of $N$, but why can't I simply use a single prime number? |
If Blum Blum Shub is modified to use a prime modulus, is it still secure? |
**I already posted this on Stackoverflow, so you might have seen this exact same question there - it was pointed out that it yould better fit here**
**This is a question about a concept that i try to wrap my head around - it is not about the specific implementation!**
I have the following scenario (simplified to ... |
Does Keyderivation with known parameters add to security? |
Why does the recommended key size between symmetric and asymmetric encryption differ greatly? |
Is symmetric encryption no longer necessary? |
How to construct the blind factors in practice? |
*I already posted this on Stack Overflow, so you might have seen this exact same question there - it was pointed out that it would better fit here.*
---
**This is a question about a concept that I try to wrap my head around; it is not about the specific implementation!**
I have the following scenario (simplifi... |
Does “key derivation” with known parameters add to security? |
First up: this is a question about a concept that I try to wrap my head around; it is not about the specific implementation. Anyway…
I have the following scenario (simplified to show the problem I have with the concept):
1. I have a symmetric master-key, lets assume the strongest algorithm out there at the time ... |
Does key derivation with known parameters add any security? |
[It is being speculated][1] that one of the ways that NSA leaker Edward Snowden may have created his "insurance policy" – distributing sensitive documents to various individuals with instructions to disseminate them should anything happen to him--is through the use of a partial key escrow.
The concept is described ... |
I'm designing a scheme for management of a small number of cryptographic keys (< 100 at any given time) and I had an idea: rather than storing all the keys, could I just store one master key and use a KDF to derive the particular key I need by varying the salt in a certain way?
For example, if I need the second enc... |
I'm Implementing a protocol that uses masking techniques (or blinding factors), so we can mask a value $y_0$ as $m_0=y_0 \cdot r_0$ where $y_0 \in \mathbb{Z}_p$ and $r_0 \stackrel {R}\leftarrow \mathbb{Z}_p$ (let $_p$ be a prime number) and the $m_0$ can be unmasked as $m_0\cdot r^{-1}_0=y_0$ at any time.
My Questio... |
Can we say that any shift cipher to be decrypted needs an algorithm of complexity “`n * n!`”? (where `n` is number of possible values. 26 in case of English language).
My reasoning related to reaching `n * n!` was as follows:
Take the word `BRAZIL` for example. We have 26 possibilities for `B`, 25 for `R, 24 for ... |
Is the complexity of Caesar (shift) ciphers “n * n!”? |
I'm Implementing a protocol that uses masking techniques (or blinding factors), so we can mask a value $y_0$ as $m_0=y_0 \cdot r_0$ where $y_0 \in \mathbb{Z}_p$ and $r_0 \stackrel {R}\leftarrow \mathbb{Z}_p$ (let $_p$ be a prime number) and the $m_0$ can be unmasked as $m_0\cdot r^{-1}_0=y_0$ at any time.
My Questio... |
I'm Implementing a protocol that uses masking techniques (or blinding factors), so we can mask a value $y_0$ as $m_0=y_0 \cdot r_0$ where $y_0 \in \mathbb{Z}_p$ and $r_0 \stackrel {R}\leftarrow \mathbb{Z}_p$ (let $_p$ be a prime number) and the $m_0$ can be unmasked as $m_0\cdot r^{-1}_0=y_0$ at any time.
My Questio... |
I have created a small cryptographic programme:
- You input your text
- A random image is generated
- Random coordinate pairs in number equal to the chars of the message are generated.
- The red component of the points at the coordinates given above is modified to become equal to the ASCII value of the lette... |
Text in random image encoder: is it flawed? |
I need to know can we use PRG of OpenSSL as a PRF? |
Is Pseudo-Random Generator (PRG) in OpenSSL uniformly distributed? |
First up: this is a question about a concept that I try to wrap my head around; it is not about the specific implementation. Anyway…
I have the following scenario (simplified to show the problem I have with the concept):
1. I have a symmetric master-key, lets assume the strongest algorithm out there at the time ... |
I'm trying to implement RSA without using any java libraries using the algorithm from wikipedia [HERE][1]
[1]: https://en.wikipedia.org/wiki/RSA_%28cryptosystem%29#Operation
So, anyone can clearly see that it is a raw RSA, and can directly be attacked.
The question is how can i include padding to the algor... |
Yes, the Pseudo Random Number Generator (PRNG) in OpenSSL is Cryptographically Secure, which means it passes statistical tests, but as @Maarten Bodewes suggests in his comment, why not go one step further and use that PRNG *directly*, rather than through OpenSSL?
OpenSSL uses EGD (which stands for Entropy Gathering ... |
I'm having a very difficult time finding a clear explanation of the parameters used elliptic curve cryptography. I know for certain that $p$ is the number or order or whatever of the given field that a particular curve uses. I know that $k$ is what is used as the secret key and that $Q=(Q_x,Q_y)$ is the public key. But... |
This web page use unusual variable names, which do not match the names you are used to see in other documents
in the calculator the curve equation is (Y^2 == X^3 + A^X + B) mod p
(many documents use a and b in lowercase)
in the calculator n is any number
(many documents use k, while n is usually the reserve... |
This web page use unusual variable names, which do not match the names you are used to see in other documents
in the calculator the curve equation is (Y^2 == X^3 + A^X + B) mod p
(many documents use a and b in lowercase)
in the calculator n is any number
(many documents use k, while n is usually the reserve... |
This web page use unusual variable names, which do not match the names you are used to see in other documents
in the calculator the curve equation is (Y^2 == X^3 + AX + B) mod p
(many documents use a and b in lowercase)
in the calculator n is any number
(many documents use k, while n is usually the reserved... |
There is an [article][1] about the provided security of the CryptDB.
The simple questions
1. Where is the row integrity?
2. Where is the completeness of the query results?
3. Where is the freshness of the data?
4. Where is the Authentication of the data?
5. What is the cost of the proxy-server, which per... |
I need to calculate the unicity distance of a block cipher. Assuming I know that the plaintext is an English message I considered using 53 as the size of the alphabet, since the message could contain lowercase ans uppercase letters from the english alphabet, as well as whitespace.
Would this be the right way to approa... |
Which characters to take into account when calculating unicity distance? |
Two very basic questions:
1. Digital Signing
------------------
**Why is it not possible to just simply replace the hash value from the request?**
Examples:
- Mallory creates two different documents A and B, that have an
identical hash value (collision).
- Mallory then sends document A t... |
> I know that k is what is used as the secret key and that $Q=(Q_x,Q_y)$ is the public key. But playing around on these two pages and seeing the contents of this file have letft me more confused. What is the importance of $P$ and how does it differ from $Q$?
Don't get too caught up with variable names. People usuall... |
Gravatar is a service that serves avatars for users based on `md5(email)`. The hash is embedded on websites, so it's public.
One of the problems with this solution is that **it's easy to track users across websites, since the same e-mail will have the same hash.**
I'm wondering if there's a cryptographic solution... |
Yes, the Pseudo Random Number Generator (PRNG) in OpenSSL is Cryptographically Secure, which means it passes statistical tests, but as @Maarten Bodewes suggests in his comment, why not go one step further and use that PRNG *directly*, rather than through OpenSSL?
OpenSSL can use EGD (which stands for Entropy Gatheri... |
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