instruction stringlengths 15 30k |
|---|
Is this algorithm acceptable? |
RC4-52 by hand / pen-and-paper? |
Hmmm, I assume that the goal of this algorithm is to provide privacy; that is, to create an encrypted message, and someone that hears this encrypted message (but not the key) is unable to recover information about the original message.
Well, your algorithm effectively divides the message into 16 byte blocks $M_1, M_... |
What data is saved in RSA private key in openssl? How to view it?
Wikpedia says [these][1] variables are saved.
[1]: http://en.wikipedia.org/wiki/RSA_%28algorithm%29#Using_the_Chinese_remainder_algorithm |
I'm being asked to use a crypto algorithm in my code, and besides the fact that I'm sure there will be implementation faults that lead to vulnerabilities, I also have concerns about the algorithm itself. I'd like to know how strongly I need to convince these guys to not use this. If it is an acceptable algorithm and th... |
I'm being asked to use a crypto algorithm in my code, and besides the fact that I'm sure there will be implementation faults that lead to vulnerabilities, I also have concerns about the algorithm itself. I'd like to know how strongly I need to convince these guys to not use this. If it is an acceptable algorithm and th... |
I need to compute a function `h^l`, where h is an element of G2 and l is a `float` number. How can this be done using the PBC library?
I have converted the `h` to an element in `G2`
As far as I have seen, for exponentiation, it has two functions :
element_pow_zn, and
element_pow_mpz
The first funct... |
I need to compute a function `h^l`, where h is an element of G2 and l is a rational number. How can this be done using the PBC library?
I have converted the `h` to an element in `G2`
As far as I have seen, for exponentiation, it has two functions :
element_pow_zn, and
element_pow_mpz
The first func... |
I'm exploring ways of encrypting Intel hex files we send to customers for flashing onto an embedded device. The embedded processor itself has a built-in mechanism that prevents anyone from reading the contents of the flash memory unless you *unlock* it using a 128-bit password.
A trivial method I thought of to encry... |
I have a homework problem:
*Explain how to find $m_{0}$ and $c$ such that $P[c=c': k \leftarrow K, c' \leftarrow E(k, m_{0})] > 0$*
where P is probability and k is chosen uniformly.
I do not know if I understand the question correctly. The notation should imply that what is the probability of the condition $c... |
The encryption scheme seems to be:
- re-use an existing 128-bit secret, originally used to unlock a read-prevention mechanism;
- split the plaintext (data to protect from prying eyes) into 128-bit blocks;
- XOR each block with that 128-bit constant.
**That approach is flawed**. Two cardinal mistakes are made:
... |
The encryption scheme seems to be:
- re-use an existing 128-bit secret, originally used to unlock a read-prevention mechanism;
- split the plaintext (data to protect from prying eyes) into 128-bit blocks;
- XOR each block with that 128-bit constant.
**That approach is flawed**. Two cardinal mistakes are made:
... |
The encryption scheme seems to be:
- re-use an existing 128-bit secret, originally used to unlock a read-prevention mechanism;
- split the plaintext (data to protect from prying eyes) into 128-bit blocks;
- XOR each block with that 128-bit constant.
**That approach is flawed**. Two cardinal mistakes are made:
... |
The encryption scheme seems to be:
- re-use an existing 128-bit secret, originally used to unlock a read-prevention mechanism;
- split the plaintext (data to protect from prying eyes) into 128-bit blocks;
- XOR each block with that 128-bit constant.
**That approach is flawed**. Two cardinal mistakes are made:
... |
I'm being asked to use a crypto algorithm in my code, and besides the fact that I'm sure there will be implementation faults that lead to vulnerabilities, I also have concerns about the algorithm itself. I'd like to know how strongly I need to convince these guys to not use this. If it is an acceptable algorithm and th... |
The [Poly1305-AES](http://cr.yp.to/mac/poly1305-20050329.pdf) paper summarizes the MAC as
$$ Poly1305(m, AES_k(n)) = {H_r(m) + AES_k(n)} \mod 2^{128} $$
Can I presume that $+$ here is just meant as a form of 16-byte mixing $H_r(m)$ and $AES_k(n)$, and that XOR would be equally effective (since both already are 1... |
Equivalents to a physical hat+shaking? |
I need to compute a function $h^l$, where h is an element of G2 and l is a rational number. How can this be done using the PBC library?
I have converted the `h` to an element in `G2`
As far as I have seen, for exponentiation, PBC has two functions :
element_pow_zn, and
element_pow_mpz
The first fun... |
I need to compute a function $h^l$, where h is an element of G2 and l is a rational number. How can this be done using the PBC library?
I have converted the `h` to an element in `G2`
As far as I have seen, for exponentiation, PBC has two functions :
element_pow_zn, and
element_pow_mpz
The first fun... |
An elliptic curve is defined over a finite field $GF(p)$
The $m$ in $(a+b\mod m)$ is equal to $p$ in $GF(p)$.
You can also read this [Elliptic Curve Cryptography - An implmentation guide][1].
It is easy-to-read and it covers most topic you will encounter during implementation.
[1]: https://www.google.com/u... |
The encryption scheme seems to be:
- re-use an existing 128-bit secret, originally used to unlock a read-prevention mechanism, as the 128-bit key;
- split the plaintext (data to protect from prying eyes) into 128-bit blocks;
- XOR each block with that 128-bit key.
**That approach is flawed**. Two cardinal mista... |
You can do RC4 using a 52-entry table, instead of a 256-entry table. All you do is change the modulo-256 arithmetic in RC4 to use modulo-52 arithmetic. There are no special changes needed, and no need to describe a special algorithm. If you want to see a description of how to perform it manually using a deck of car... |
Should the secret message of Shamir's secret-sharing algorithm be interpreted and processed byte by byte?
Interpreting it byte by byte makes it easier to process, but in case one of the shareholders decides to tamper with some of the bytes in his possession, this will affect the secret reconstruction.
This is a seri... |
Should the secret key of Shamir's secret-sharing algorithm be interpreted byte by byte? |
>Does matching all the test vectors mean my implementations are valid mathematically?
Basically the comments got it, but test vectors are designed to attempt to hit lots of cases, but with high probability will not catch every single mistake. Should you do it? Definitely. Does it mean everything is perfect? No.
>... |
The encryption scheme seems to be:
- re-use an existing 128-bit secret, originally used to unlock a read-prevention mechanism, as the 128-bit key;
- split the plaintext (data to protect from prying eyes) into 128-bit blocks;
- XOR each block with that 128-bit key.
**That approach is flawed**. Two cardinal mista... |
Assume Alice and Bob are using RSA to create a common session key and Cindy is listening, attempting to obtain the session key.
Alice and Bob each have their public- and private-key pairs ($\left[pub_{A}, pri_{A}\right]$ for Alice and $\left[pub_{B}, pri_{B}\right]$ for Bob) and Alice, Bob, and Cindy all know everyo... |
Is a known plaintext, ciphertext, and public-key a viable attack on RSA? |
[PKCS#1][1] is one of the most used (de-facto) standard for real-world use of RSA.
It was updated in October 2012, and published as PKCS#1 v2.2 by February 2013. Changes include:
- incorporation of erratas (last updated in 2005) to PKCS#1 v2.1 (last updated in 2002);
- additional hashes of the SHA-2 family, incl... |
What changed in PKCS#1 v2.2, and why? |
[PKCS#1][1] is one of the most used (de-facto) standard for real-world use of RSA.
That's for good reasons: PKCS#1 is well thought, versatile, understandable, was relatively stable for over two decades, and remains practically secure in its original form, contrary to some other standardized use of RSA (the ISO/IEC 9... |
They are not using any exotic encryption. In fact I don't even think they are doing any encryption, just 1:1 mapping (tokenization) after lowering the case on plain text data. For details, I did some basic crypt-analysis on a still from their [publicly visible demo video][1].
[images removed due to DMCA request]
... |
[PKCS#1][1] is one of the most used (de-facto) standard for real-world use of RSA.
That's for good reasons: PKCS#1 is well thought, versatile, understandable, has been relatively stable for over two decades, and remains practically secure in its original form, contrary to some other standardized uses of RSA (like th... |
I want to divide a system that maintains these properties, based on [Shamir's Secret Sharing][1]:
1. A secret key is split up to N pieces, where T of them are enough to reconstruct the key.
2. The original key is then destroyed and doesn't exist anywhere except the N separate pieces.
3. The information unlocked by... |
Is there a way to use Shamir Secret Sharing with updatable data? |
I am just curious. We have a group $G$ and its subgroup $H$ with a generator element $h \in H$. How difficult is it to check for $x \in G$ that $x \in \langle h \rangle$? Is there a better way than testing $x \equiv h^1,\ x \equiv h^2,\ x \equiv h^3,\ ...$? |
How difficult is it to check if a group element is in a sub group? |
I have an RSA group with modulus $n = p \cdot q$, two safe primes $p=2p'+1$ and $q=2q'+1$ and the "public" and "private" key exponents $d$ and $e$. $\phi(n) = 4p'q'$ is the order of the RSA group. If I know $\phi(n)$ I can calculate $p$ and $q$. I ask myself what is if I know $e$ and $d$ (and $m$ and $n$) with $m^{d \c... |
Is it possible to determine the group order by knowing the "public" and "private" key exponents in an RSA group? |
I am just wondering what is the most common, or most used, block cipher mode used to goes with CTS?
ECB or CBC? |
I'm trying to understand [Feldman's VSS Scheme][1]. The basic idea of that scheme is that one uses Shamir secret sharing to share a secret and commitments of the coefficients of the polynomial to allow the other party to verify that the share they received is valid. I implemented it in code following the wikipedia page... |
In a paper it says: "To convince a verifier that a group element is a quadratic residue, the prover executes the following proof with the verifier":
$PK \left\{ (\alpha) : y = \pm g^\alpha \right\}$
Does someone know how such proof is implemented by a signature proof of knowledge? The group is an RSA group $\math... |
Zero-knowledge proof that a group element is a quadratic residue? |
I'm trying to understand [Feldman's VSS Scheme][1]. The basic idea of that scheme is that one uses Shamir secret sharing to share a secret and commitments of the coefficients of the polynomial to allow the other party to verify that the share they received is valid. I implemented it in code following the wikipedia page... |
Bob know's Alice's public key, and he wants to make sure he's connecting to the one which has that key. Furthermore, Alice wants to verify when she gets a connection from Bob who'll give his public key that he is indeed the one who has that key.
Bob will send Alice half the AES private key and half the initializatio... |
Is this method for exchanging private key using RSA sound? |
Suppose that p is a safe prime of 2048 bits (p=2q+1, and q is prime).
Suppose that one is given two pairs (x1,y1) and (x2,y2) such that:
y1=x1^r1 (mod p)
y2=x2^r2 (mod p)
Where r1 and r2 are unknowns.
Is it easy or hard to check if r1=r2 without further knowledge ? Does this problem have a name?
Is ther... |
Can one detect if two pairs of elements in Zp have the same exponential relation? |
This is another way of expressing the decisional Diffie-Hellman problem. This problem is more typically written as 'given $g,\ g^a, g^b, g^c$, does $g^{ab} = g^c$?'.
As for the difficulty of this problem, it is believed to be difficult as long as you stay within a large prime subgroup; in this case (because you sp... |
Can someone explain how to find inverses in truncated polynomial rings manually with handwriting :
as an example from the tutorial,
> Example. Take N=7, q=11, a=3+2X2-3X4+X6. The inverse of a modulo 11 is
> A=-2+4X+2X2+4X3-4X4+2X5-2X6, since
>
> (3+2X2-3X4+X6)*(-2+4X+2X2+4X3-4X4+2X5-2X6) = -10+22X+22X3-22X6 = ... |
In AES modes of encryption on input a plaintext of $N$ blocks (We assume that the input is always a multiple of the blockcipher mode: $n*16$b) the size of the ciphertext is $N+1$ where the extra block is the IV. Is there an efficient way to have variable length output on variable length input. I.e: $16$bytes of plainte... |
Is there an efficient way to have variable length output on variable length input of a blockcipher? |
Can someone explain how to find inverses in truncated polynomial rings manually with handwriting :
as an example from the tutorial,
> Example. Take $N=7$, $q=11$, $a=3+2X^2-3X^4+X^6$. The inverse of $a \bmod 11$ is
> $a^{-1}=-2+4X+2X^2+4X^3-4X^4+2X^5-2X^6$, since
>
> $(3+2X^2-3X^4+X^6)*(-2+4^X+2X^2+4X^3-4X^4+2... |
Can someone explain how to find inverses in truncated polynomial rings manually with handwriting :
as an example from the tutorial,
> Example. Take $N=7$, $q=11$, $a=3+2X^2-3X^4+X^6$. The inverse of $a \bmod 11$ is
> $a^{-1}=-2+4X+2X^2+4X^3-4X^4+2X^5-2X^6$, since
>
> $(3+2X^2-3X^4+X^6)*(-2+4^X+2X^2+4X^3-4X^4+2... |
I am trying to find the protocol with the least overhead, which still meets the following requirements:
- Server Authentication of server identity to client. The client has an authentic copy of the server long term public key.
- Perfect Forward Secrecy.
- Confidentiality, integrity, authenticity of payload, inc... |
Our assignment asks us to convert an RSA speed in bytes per second to a DES speed in bytes per second. Our professor's treatment of this ("RSA is 100 times slower than DES") seems insufficient. Could anyone explain how this conversion is calculated?
Thanks. |
Suppose that $p$ is a safe prime of 2048 bits ($p = 2q + 1$, and $q$ is prime).
Suppose that one is given two pairs $(x_1, y_1)$ and $(x_2, y_2)$ such that:
$y_1 = x_1^{r_1} \pmod p$
$y_2 = x_2^{r_2} \pmod p$
Where $r_1$ and $r_2$ are unknowns.
Is it easy or hard to check if $r_1 = r_2$ without further kno... |
That is, if I generate every possible result, and analyze the structure against, for example, a dictionary, won't that identify which of the solutions in the domain is most likely the correct one?
I realize the numbers involved, but this does ultimately reduce the problem to a hardware one. If this is not true, then... |
Isn't the structure of a potential plaintext of a ciphertext generated by a one-time pad dispositive, cryptanalysis-wise? |
The system requires to be as paranoid as possible regarding security. One of the few contemplated changes to the current design is to use multiple encryption. First proposal was to use Serpent on top of AES-256, but after looking into it, it seems like a triple AES could also serve the purpose.
So the options are:
... |
Would a "Triple AES" (in the sense of how Triple Des works) serve for a dramatic increase in safety? |
What would be the best way of encrypting small mesasages to be stored in encrypted form? (This sounds like somthing a textbook would cover, but I haven't found any references).
Let's say I have many systems producing messages (log-lines) which I would like to transfer and store centrally in a secure manner. Using of... |
This is a trivial question, but I had to ask:
since each generated share in a Shamir's secret sharing scheme initially consists of a pair of values (representing the coordinates of a point on the plane), how do I reduce the two values to one, so that the share that I eventually hand out will consist of only one valu... |
This is a trivial question, but I had to ask:
since each generated share in a Shamir's secret sharing scheme initially consists of a pair of values (representing the coordinates of a point on the plane), how do I reduce the two values to one, so that the share that I eventually hand out will consist of only one valu... |
I'm looking for the cryptographic equivalent of a Drivers license where the issuer can be verified, the issuer doesn't need to know who you showed the drivers license to, but also allows per-transaction privacy.
Mentally assume that the private keys for this trust are securely stored on hardware (SIM, SmartCard etc)... |
I'm looking for the cryptographic equivalent of a Drivers license where the issuer can be verified, the issuer doesn't need to know who you showed the drivers license to, but also allows per-transaction privacy.
Mentally assume that the private keys for this trust are securely stored on hardware (SIM, SmartCard etc)... |
I'm looking for the cryptographic equivalent of a Drivers license where the issuer can be verified, the issuer doesn't need to know who you showed the drivers license to, but also allows per-transaction privacy.
I would use the standard PKI system, but there is a hard coded certificate serial number in each cert, re... |
Lets assume
* a 4gig file that is internally made of 1 million pages of 4k bytes each (page).
* the file was originally AES-GCM encrypted
* these pages (or entire file) lives across the internet i.e. individual page reads are expensive/slow. (network IO operations are at page level by the way)
Is there any... |
Partial decryption of large file in AES-GCM (or other modes)? |
If Bob and Charlie will share a secret, then it information-theoretic anonymity might
<br>
be possible, otherwise the best that can be hoped for is computational anonymity.
<br>
I haven't come up up with any way to achieve information-theoretic anonymity when
<br>
Bob and Charlie share a secret, so I will only be... |
If Bob and Charlie will share a secret, then it information-theoretic anonymity might
<br>
be possible, otherwise the best that can be hoped for is computational anonymity.
<br>
I haven't come up up with any way to achieve information-theoretic anonymity when
<br>
Bob and Charlie share a secret, so I will only be... |
Chinese "looks" encrypted. I believe it to be a marketing gimmick; they want to be able to show "encrypted text" that people will unconsciously associate with notions of unreadability and utter obscurity -- and nothing beats Chinese for that (except in China, of course; if they want to sell their product to China they ... |
I came across a marketing video [here][1]. They claim to perform AES encryption and tokenization of sensitive data, at the corporate gateway, before it leaves the company firewall destined for the public cloud. So keys and *token<=>plain text* mapping tables remain at gateway and cipher text/tokens live in the public c... |
If Bob and Charlie will share a secret, then it information-theoretic privacy might
<br>
be possible, otherwise the best that can be hoped for is computational anonymity.
<br>
I haven't come up up with any way to achieve information-theoretic privacy when
<br>
Bob and Charlie share a secret, so I will only be add... |
In block cipher modes of operation for encryption on input of a plaintext of $N$ blocks (We assume that the input size is always a multiple of the blockcipher mode: $N·16$ bytes) the size of the ciphertext is $N+1$, where the extra block is the IV.
Is there an efficient way to have fixed (parametrizable) larger leng... |
Is there an efficient way to hide the encrypted plaintext length with a block cipher? |
I'm studying UProve, and one of the fundamental components of this technology is based upon the relationship between
> i^Q mod P = 1
Lacking a specific name I can call this mathematical relationship, where can I learn more about this equation?
I've heard that not only will the equation equal one, but there a... |
What is the significance of i^Q mod P = 1 and are there any special properties to be aware of? |
I'm studying UProve, and one of the fundamental components of this technology is based upon the relationship between
> i^Q mod P = 1
Lacking a specific name I can call this mathematical relationship, where can I learn more about this equation?
I've heard that not only will the equation equal one, but there a... |
If Bob and Charlie will share a secret, then it information-theoretic privacy might
<br>
be possible, otherwise the best that can be hoped for is computational anonymity.
<br>
I haven't come up up with any way to achieve information-theoretic privacy when
<br>
Bob and Charlie share a secret, so I will only be add... |
heres the full paper:
http://www-users.cs.umn.edu/~jansen/papers/lira-ndss2013.pdf
Proportionally differentiated services
are the foundation for incentives: users who choose to run
relays will be able to proportionally increase their performance
relative to those not contributing. Further, relays may con-
tri... |
Can a LIRA (Lightweight Incentivized Routing for Anonymity) system work with cjdns or other alternative decentralized networks/meshnets? |
One example of a DLP based crypto system (or rather DDH based crypto system) where the public key parameters include two independent generators of the subgroup, is [Cramer Shoup][1]. Since the security proof of this scheme is based on DDH, it seems at least one of the two generators has to be uniformly chosen anew for ... |
heres the full paper:
http://www-users.cs.umn.edu/~jansen/papers/lira-ndss2013.pdf
Proportionally differentiated services
are the foundation for incentives: users who choose to run
relays will be able to proportionally increase their performance
relative to those not contributing. Further, relays may con-
tri... |
I am developing a mostly-offline authorization system that authorizes a user using an deterministically generated AuthKey derived from a MasterKey derived from a high-entropy chunk of data (128 bits) and a low entropy data (for example, an email address).<br>
The total length of the concatenated data will never be mor... |
How to perform the Multiplicative Inverse Modulo in International Data Encryption Algorithm?
I cannot understand on how to perform it...
ex. I have a value of **"cf80"** and the value that is appearing to me is this - **"a5ec"**
this is the thing that I've done based on my understanding
**answer = 23060 % 655... |
How to perform the Multiplicative Inverse Modulo in International Data Encryption Algorithm?
I cannot understand on how to perform it...
ex. I have a value of **"cf80"** and the value that is appearing to me is this - **"3080"**
this is the thing that I've done based on my understanding
**answer = 53120 % 655... |
How to perform the Multiplicative Inverse Modulo in International Data Encryption Algorithm?
I cannot understand on how to perform it...
ex. I have a value of **"cf80"** and the value that is appearing to me is this **"3080"**
this is the thing that I've done based on my understanding
**answer = 53120 % 6553... |
I am developing a mostly-offline authorization system that authorizes a user using an deterministically generated AuthKey derived from a MasterKey derived from a high-entropy chunk of data (128 bits) and a low entropy data (for example, an email address).<br>
The total length of the concatenated data will never be mor... |
I am developing a mostly-offline authorization system that authorizes a user using an deterministically generated AuthKey derived from a MasterKey derived from a high-entropy chunk of data (128 bits) and a low entropy data (for example, an email address).<br>
The total length of the concatenated data will never be mor... |
Ars technica posted an [article][1] about the latest in cyber warfare from the stuxnet crew.
They key stretched MD5 by iterating it 10,000 times. It seems to be effective at handicapping HashCat's gpu acceleration. Had I been them I would have used bcrypt instead.
Why/When would someone prefer streched-md5 over... |
One example of a DLP based crypto system (or rather DDH based crypto system) where the public key parameters include two independent generators of the subgroup, is [Cramer Shoup][1]. Since the security proof of this scheme is based on DDH, it seems at least one of the two generators has to be uniformly chosen anew for ... |
One example of a DLP based crypto system (or rather DDH based crypto system) where the public key parameters include two independent generators of the subgroup, is [Cramer Shoup][1]. Since the security proof of this scheme is based on DDH, it seems at least one of the two generators has to be uniformly chosen anew for ... |
I know confusion is used in cryptography to complicate identification of relationship between the cipher text and the symmetric key, but I want to know when the confusion is applied during encryption (i.e.)
1.) Confusion applied on the symmetric key[`K1`] to form the modified symmetric key[`K2`] and then `K2` is use... |
When confusion is applied during encryption? |
Considering a scenario of anonymous data transfer between seller and buyer using proxies. If we consider that there are three proxies that are being selected by buyer to obtain data from different sellers(like in emule), how can we make sure that these proxies do not collude with each other to obtain the copy that is b... |
I'm designing a [protocol](https://raw.github.com/freelan-developers/libfscp/master/fscp.txt) for use into a VPN software.
The VPN frames are encapsulated into AES-256 CBC encrypted frames. I understand that IVs must be uniquely used for each message encrypted with the same key. I believe that usually protocols gene... |
What are the constraints for an IV using AES in CBC mode? |
One example of a DLP based crypto system (or rather DDH based crypto system) where the public key parameters include two independent generators of the subgroup, is [Cramer Shoup][1]. Since the security proof of this scheme is based on DDH, it seems at least one of the two generators has to be uniformly chosen anew for ... |
Reading Goldreich's Foundations of Cryptography II, I found this proof for the security of the common pseudorandom generator + XOR encryption scheme (Proposition 5.2.12 in the book):
Assume you have a secure pseudorandom generator $g \colon \lbrace 0,1 \rbrace^n \to \lbrace 0,1 \rbrace^m$, and you construct your enc... |
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