instruction stringlengths 15 30k |
|---|
From TLS SRP spec [RFC 5024](http://tools.ietf.org/pdf/rfc5054.pdf) 'x' which is then used to calculate verifier is calculated as follows:
x = SHA1(s | SHA1(I | ":" | P))
I thought about removing 'I' to facilitate changing of user names(verifier won't have to be recalculated). However I'm not sure if it will... |
Why is TLS SRP verifier based on user name? |
I have a message M1 and I want to encrypt it by XORing it with two keys K1 and K2, giving as result K3. So far so good.
Now I was wondering if I could create a "fake" result K4, by XORing a different message M2 with the same keys K1 and K2, giving as result K4. This way, if I'm forced to handle K3, I can give K4 ins... |
There is some intriguing things about DES and 3DES. Now, I know that DES is weak and 3DES was an attempt to construct a more secure block-cipher from a deprecated one.
Having this in mind, what about the composition of two independent instantiations of block-cipher (t.i.t.s with two independent keys) having a reduc... |
There is some intriguing things about DES and 3DES. Now, I know that DES is weak and 3DES was an attempt to construct a more secure block-cipher from a deprecated one.
Having this in mind, what about the composition of two independent instantiations of block-cipher (t.i.t.s with two independent keys) having a reduc... |
Best courses (handbooks, tutorials) about proofs of security? |
I have a message $m_1$ and I want to encrypt it by XORing it with two keys $k_1$ and $k_2$:
$$c_1 = m_1 \oplus k_1 \oplus k_2$$
So far so good.
Now I was wondering if I could create a "fake" result with a different message $m_2$:
$$c_2 = m_2 \oplus k_1 \oplus k_2$$
This way, if I'm forced to hand over $c... |
From TLS SRP spec [RFC 5024](http://tools.ietf.org/pdf/rfc5054.pdf) 'x' which is then used to calculate verifier is calculated as follows:
x = SHA1(s | SHA1(I | ":" | P))
I thought about removing 'I' to facilitate changing of user names(verifier won't have to be recalculated). Then x will be:
x = SHA1... |
I'm looking for the best course material on the subjet of proofs, reductions between games. I've read the lessons from Wagner, Bellare and Goldwasser but I'm looking for a thing which is very exhaustive (with details) to understand all subtleties.
I've seen slides from D. Pointcheval, but the slides are not sufficie... |
I want to implement some of the basic encryption algorithms on smart card, could any body guide me, how to program a smart card, which tools (hardware and software) i should have ,and are these tools are free?
further i need to explore, is it possible to implement Bi-linear pairing on smart cards or ECC algorithms?
... |
I don't understand why TLS SRP includes user name in verifier calculation, given that user name is basically public. From spec [RFC 5024](http://tools.ietf.org/pdf/rfc5054.pdf) 'x' which is then used to calculate verifier is calculated as follows:
x = SHA1(s | SHA1(I | ":" | P))
I thought about removing 'I' ... |
[I found this article on SO, but the answer was short, and the subject was closed][1],
What i dont understand, is which one of the two limits memory usage to avoid custom Hardware to break the password?
[1]: http://stackoverflow.com/questions/1226513/whats-the-advantage-of-scrypt-over-bcrypt |
Bcrypt VS Scrypt, Again? |
Bcrypt use Blowfish to crypt a derived key from the passphrase, Blowfish is a cryptographic algorithm, but [here it is said that][1]:
> Note that
Salsa20/8 Core is not a cryptographic hash function since it is not
collision-resistant.
so how this is useful is Scrypt?
[1]: http://tools.ietf.org/html/... |
How Scrypt uses Salsa? |
I have a message $m_1$ and I want to encrypt it by XORing it with two keys $k_1$ and $k_2$:
$$c_1 = m_1 \oplus k_1 \oplus k_2$$
So far so good.
Now I was wondering if I could create a "fake" result with a different message $m_2$:
$$c_2 = m_2 \oplus k_1 \oplus k_2$$
This way, if I'm forced to hand over $c... |
I am trying to understand the sha-256 algorithm from http://csrc.nist.gov/publications/fips/fips180-2/fips180-2.pdf . I understood the padding and parsing of the message string. However after that it states:
For i = 1 to N:
{
1. Prepare the message schedule, {Wt}:
Wt=Mt(i) 0 <=t <= 15
Wt=RO... |
I found [this article][1] on SO, but the answer was short, and the subject was closed,
What i don't understand, is:
Which one of the two limits memory usage to avoid custom Hardware to break the password?
[1]: http://stackoverflow.com/questions/1226513/whats-the-advantage-of-scrypt-over-bcrypt |
I'm looking for the best course material on the subjet of proofs, reductions between games... What are the various methodologies ? What are the preferred ones ? In what cases we use a method rather than another ?
Thank you very much. |
I'm trying to implement lightweight yet secure protocol for communicating two trusted parties with each other.
Consider following scheme:
> Alice wants to establish secure two-sided channel with Bob.
> Alice knows Bob's public key from reliable source, so she generates random symmetric key, encrypts it with Bo... |
I've read that we can study the security of modes of operation by assuming the use of an ideal block cipher. I've also seen a paper suggesting that the ideal cipher model could be something else than an ideal block cipher.
Is there protocols relying on a mode of encryption and whose the proof has been done by assumi... |
I've read that we can study the security of modes of operation by assuming the use of an ideal block cipher. I've also seen a paper suggesting that the ideal cipher model could be something else than an ideal block cipher.
Are there protocols relying on a mode of encryption and whose the proof have been done by assu... |
I've read that we can study the security of modes of operation by assuming the use of an ideal block cipher. I've also seen a paper suggesting that the ideal cipher model could be something else than an ideal block cipher.
Are there protocols relying on an encryption mode and whose the proofs have been done by assum... |
I found [this article][1] on SO, but the answer was short, and the subject was closed,
What i don't understand, is:
Which one of the two limits memory usage to avoid custom Hardware to break the password?
Edit: there is an excellent discussion for beginners like me [here][2]:
[1]: http://stackoverflow.c... |
I have a message $m_1$ and I want to encrypt it by XORing it with two keys $k_1$ and $k_2$:
$$c_1 = m_1 \oplus k_1 \oplus k_2$$
So far so good.
Now I was wondering if I could create a "fake" result with a different message $m_2$:
$$c_2 = m_2 \oplus k_1 \oplus k_2$$
This way, if I'm forced to hand over $c... |
I'm in the middle of planning a 5000ish word essay on fully homomorphic cryptography, the current practical implementations and their limitations.
Which areas of CS as a subject have been (or will be) most affected or will utilise fully homomorphic cryptography the most in the coming years and developments?
Thank... |
Which areas in CS will be (or have been) most affected by fully homomorphic cryptography? |
I'm in the middle of planning a 5000ish word essay on fully homomorphic cryptography, the current practical implementations and their limitations.
Which areas of CS as a subject have been (or will be) most affected or will utilise fully homomorphic cryptography the most in the coming years and developments? |
To allow effective cryptanalysis of a scheme, two things must be clear: first, our goal (e.g., what we want to keep secret, what we want to preserve the integrity of, etc.), and second, what the attacker(s) are allowed to know or do.
So, our goal is to preserve the secrecy of $m_1$, I take it. So, the attacks will ... |
I'm thinking about buying a USB TRNG. How do I evaluate it's randomness? I'm sure some are better than others but which is which? Are thermal-noise better than radio-noise TRNGs? |
I'm thinking about buying a USB TRNG. How do I evaluate its randomness? I'm sure some are better than others but which is which? Are thermal-noise better than radio-noise TRNGs? |
I have a trusted third part A that issues an access token (xml file) to an untrusted client C that uses this token to log into an untrusted server S and access to the authorized files.
I want only that C can't manipulate the token changing the permissions stored inside.
I had thought to digitally sign the token wit... |
What kind of cryptography should i use? |
am sorry, an a beginner, so please forgive me if i make mistakes, so here is what i understood:
PBKDF2: uses HMAC, so, the message is the password, and the key that crypts the message is the salt? or is it the inverse?
so i guess the second one, because the user will write the password, and then the program will ... |
am sorry, an a beginner, so please forgive me if i make mistakes, so here is what i understood:
PBKDF2: uses HMAC, so, the message is the password, and the key that crypts the message is the salt? or is it the inverse?
so i guess the second one, because the user will write the password, and then the program will ... |
am sorry, an a beginner, so please forgive me if i make mistakes, so here is what i understood:
PBKDF2: uses HMAC, so, the message is the password, and the key that crypts the message is the salt? or is it the inverse?
so i guess the second one, because the user will write the password, and then the program will ... |
am sorry, an a beginner, so please forgive me if i make mistakes, so here is what i understood:
PBKDF2: uses HMAC, so, the message is the password, and the key that crypts the message is the salt? or is it the inverse?
so i guess the second one, because the user will write the password, and then the program will ... |
am sorry, an a beginner, so please forgive me if i make mistakes, so here is what i understood:
PBKDF2: uses HMAC, so, the message is the password, and the key that crypts the message is the salt? or is it the inverse? and this is done the number of the rounds n times.
so i guess the second one, because the user ... |
What is the state of the art way when implementing a scheme challenging a party to proof they have access to certain data?
What I'm looking for something along the lines of
.) Give them (id-some-data, seed, my pub-key)
request to return (some-data xor seed, signed with my-pub key)
.) Give them (id-some-dat... |
"proof of access" schemes? |
What is the state of the art way when implementing a scheme challenging a party to proof they have access to certain data?
What I'm looking for something along the lines of
.) Give them (id-some-data, random-data, my pub-key)
request to return signature of (some-data xor random-data, signed with my-pub key)
... |
I don't understand why TLS SRP (or SRP in general) includes the user name in verifier calculation, given that user name is basically public.
From spec [RFC 5054](http://tools.ietf.org/html/rfc5054#section-2.4) $x$, which is then used to calculate verifier, is calculated as follows:
x = SHA1(s | SHA1(I | ":" ... |
I am trying to understand the sha-256 algorithm from [FIPS 180-2](http://csrc.nist.gov/publications/fips/fips180-2/fips180-2.pdf). I understood the padding and parsing of the message string. However after that it states (page 15):
> For $i = 1$ to $N$:
> {
>
> 1. Prepare the message schedule, ${W_t}$:... |
What does "message schedule" mean in SHA-256? |
I'm looking for course material on the subject of proofs, reductions, and games, as used to prove cryptographic schemes secure. What are the methodologies? What are the preferred ones? In what cases is it best to use a method rather than another? |
I'm trying to reverse engineer key exchange protocol and faced with the following problem:
Protocol is based on Diffie-Hellman key exchange method:
**g** - generator
**m** - modulus
Alice:
**a** - private key
$A \equiv g^a\pmod{m}$ - public key
Bob:
**b** - private key
$B \equiv g^b\pmod{m}$ ... |
Is this a sensible scheme for 2-way client/server communication? A client connects to a server. The server and client both generate RSA keys, and send over the public ones to each other. If the client wants to send a message, they encrypt it with the server's public key, send it over, and the server decrypts it. Vice v... |
Amateur question: two-way RSA? |
am sorry, an a beginner, so please forgive me if i make mistakes, so here is what I understood:
**PBKDF2:** uses HMAC, so, the message is the password, and the key that crypts the message is the salt? or is it the inverse? and this is done the number of the rounds $n$ times.
So I guess the second one, because the... |
I have a message $m_1$ and I want to encrypt it by XORing it with two keys $k_1$ and $k_2$:
$$c_1 = m_1 \oplus k_1 \oplus k_2$$
So far so good.
Now I was wondering if I could create a "fake" result with a different message $m_2$:
$$c_2 = m_2 \oplus k_1 \oplus k_2$$
This way, if I'm forced to hand over $c... |
Given:
- **H** is a good hash function with block size **L**.
- **K** is a key of length >= L (recommended by [RFC 2104][1]).
- **K<sub>hex</sub>** and **K<sub>base64</sub>** are ASCII encodings of K.
In the HMAC algorithm, **is there a good reason to prefer K** over the other encodings?
Obviously the HMA... |
When using HMAC, does key encoding matter? |
I'm interested by the compositions of the block cipher DES, instantiated with independent keys $k_1$, $k_2$ and $k_3$.
Are these 3 compositions equivalent in terms of security ?
$$DES_{k_1}(DES_{k_2}(DES_{k_3}(.)))$$
$$DES_{k_1}(DES_{k_2}(DES^{-1}_{k_3}(.)))$$
$$DES_{k_1}(DES^{-1}_{k_2}(DES^{-1}_{k_3}(.)))$$
T... |
Have these compositions of block ciphers the same security? |
I'm interested by the compositions of the block cipher DES, instantiated with independent keys $k_1$, $k_2$ and $k_3$.
Are these 3 compositions equivalent in terms of security ?
$$DES_{k_1}(DES_{k_2}(DES_{k_3}(.)))$$
$$DES_{k_1}(DES_{k_2}(DES^{-1}_{k_3}(.)))$$
$$DES_{k_1}(DES^{-1}_{k_2}(DES^{-1}_{k_3}(.)))$$
T... |
I'm interested by the compositions of the block cipher DES, instantiated with independent keys $k_1$, $k_2$ and $k_3$.
Are these 3 compositions equivalent in terms of security ?
$$DES_{k_1}(DES_{k_2}(DES_{k_3}(.)))$$
$$DES_{k_1}(DES_{k_2}(DES^{-1}_{k_3}(.)))$$
$$DES_{k_1}(DES^{-1}_{k_2}(DES^{-1}_{k_3}(.)))$$
T... |
My secure multi-party computation (MPC) in need is simply to determine if a sum of two private variable is bigger than a given value $y$, as
$f(x_0, x_1) = [(x_0 + x_1) > y]$
in which the value of sum itself (i.e., $x_0+x_1$) is deemed private and $y$ is publicly known.
I am aware of many MPC protocols out t... |
What's the most efficient MPC protocol to determine if sum's bigger than y? |
My secure multi-party computation (MPC) in need is simply to determine if a sum of two private variable is bigger than a given value $y$, as
$f(x_0, x_1) = [(x_0 + x_1) > y]$
in which the value of sum itself (i.e., $x_0+x_1$) is deemed private and $y$ is publicly known. The output of this function is ``yes`` or ... |
What's efficient MPC protocol for determining if sum's bigger than y? |
Is it possible to anonymize web traffic so that the IP Address cannot be determined? |
Is it possible to anonymize web traffic so that the IP Address cannot be determined while still being able to determine distinct IPs? |
What is the state of the art way when implementing a scheme challenging a party to proof they have access to certain data?
What I'm looking for something along the lines of
1. Give them (id-some-data, random-data, my public-key).
Request to return the signature of (some-data xor random-data) with my-publ... |
What is the state of the art way when implementing a scheme challenging a party to prove they have access to certain data?
What I'm looking for something along the lines of
1. Give them (id-some-data, random-data, my public-key).
Request to return the signature of (some-data xor random-data) with my-publ... |
Suppose I have a 2048 bit RSA public key, and want to brute force the corresponding private key. I guess there are 2048^16 possible combinations?
How long would this take me to brute force with an i7, with a GPU, and with Amazon Cloud?
Is there any benchmarking data, that can be used to calculate similar for a 16... |
If I encrypt a string with a public key - does the encrypted package reveal the public key I used to encrypt it? Basically, I don't want anyone to know who the package is addressed too.
I'm thinking about RSA, but also interested in DSA. |
Can you Identify the public key used to encrypt something? |
I'm interested by the compositions of the block cipher DES, instantiated with independent keys $k_1$, $k_2$ and $k_3$.
Are these 3 compositions equivalent in terms of security?
$$DES_{k_1}(DES_{k_2}(DES_{k_3}(.)))$$
$$DES_{k_1}(DES_{k_2}(DES^{-1}_{k_3}(.)))$$
$$DES_{k_1}(DES^{-1}_{k_2}(DES^{-1}_{k_3}(.)))$$
I'... |
If I encrypt a string with a public key, does the encrypted ciphertext reveal the public key I used to encrypt it? Basically, I don't want anyone to know who the ciphertext is addressed to.
I'm thinking about RSA, but also interested in DSA. |
Can you identify the public key used to encrypt something? |
How much computing time on a typical desktop computer would it take to find a new length and new data to extend a text file of about 10K Bytes with a given MD5 hash? |
length extension attack on an MD5 hash of a text file of about 10K Bytes? |
Differential privacy defines "privacy" of a mechanism $A$ as the "closeness" of the two distribution $Pr[A(D) \in S]$ and $Pr[A(D') \in S]$ where $D,D'$ differ in one element. And the _distance_ between these distributions is multiplicative, i.e.
$\left| \frac{Pr[A(D) \in S]}{Pr[A(D') \in S]} \right| \leq e^\epsilo... |
I'm pretty sure I understand textbook RSA.
- Choose *p* and *q,* large primes, and compute *n=pq.*
- Choose *e* such that *gcd(phi(n),e)=1.*
- Publish *n* and *e.*
- Compute *d* such that *de=1* *(mod phi(n)).*
- To encrypt a message **M**, compute *E=**M**^e (mod n).*
- To decrypt, compute D=E^d (mod n),... |
I'm pretty sure I understand textbook RSA.
- Choose *p* and *q,* large primes, and compute *n=pq.*
- Choose *e* such that $gcd(\phi(n),e)=1.$
- Publish *n* and *e.*
- Compute *d* such that $de=1$ (mod $\phi(n)$).
- To encrypt a message **M**, compute *E=**M**^e (mod n).*
- To decrypt, compute *D=E^d (mod ... |
It depends on what you are using RSA for and how deep of an understanding you would like.
A sort of general overview of RSA and potential attacks against textbook RSA is presented in the [*Handbook of Applied Cryptography*](http://cacr.uwaterloo.ca/hac/), specifically [chapter 8](http://cacr.uwaterloo.ca/hac/about/c... |
Craig Gentry's thesis (reference below) talks about circuit privacy being straight forward from fully homomorphic encryption in the last chapter.
Can somebody explain in simpler terms what that means ? i have read it couple of times but could not get it .
[Gentry, Craig. A fully homomorphic encryption scheme. Dis... |
Can any one explain Circuit Privacy using fully homomorphic encryption from Gentry's thesis? |
It depends on what you are using RSA for and how deep of an understanding you would like.
A sort of general overview of RSA and potential attacks against textbook RSA is presented in the [*Handbook of Applied Cryptography*](http://cacr.uwaterloo.ca/hac/), specifically [chapter 8](http://cacr.uwaterloo.ca/hac/about/c... |
[Craig Gentry's thesis][1] talks about circuit privacy being straight forward from fully homomorphic encryption in the last chapter.
Can somebody explain in simpler terms what that means ? I have read it couple of times but could not get it.
[1]: http://crypto.stanford.edu/craig/craig-thesis.pdf |
[Craig Gentry's thesis][1] talks about circuit privacy being straight forward from fully homomorphic encryption in the last chapter.
Can somebody explain in simpler terms what that means ? I have read it couple of times but could not get it. While the definition of Circuit privacy is simple the realization of the sa... |
If I encrypt a string with a public key, does the encrypted ciphertext reveal the public key I used to encrypt it? Basically, I don't want anyone to know who the ciphertext is addressed to.
I'm thinking about RSA, but also interested in DSA. The ciphertext is not known. |
My secure multi-party computation (MPC) in need is simply to determine if a sum of two private variable is bigger than a given value $y$, as
$f(x_0, x_1) = [(x_0 + x_1) > y]$
in which the value of sum itself (i.e., $x_0+x_1$) is deemed private and $y$ is publicly known. The output of this function is ``yes`` or ... |
**The problems:**
* The Discrete Logarithm problem: Given $y$, find $x$ so that $g^x = y$.
* The Computational Diffie-Hellman problem: Given $y_1 = g^{x_1}$ and $y_2 = g^{x_2}$ (but not $x_1$ and $x_2$), find $y = g^{x_1·x_2}$.
* The Decisional Diffie-Hellman problem: Given $y_1, y_2, y_3$, decide if they are of t... |
[NIST SP 800-57](http://csrc.nist.gov/publications/nistpubs/800-57/sp800-57_part1_rev3_general.pdf) specifies a correspondence between RSA modulus size $n$ and expected security strength $s$ in bits:
Strength RSA modulus size
80 1024
112 2048
128 3072
192 768... |
[NIST SP 800-57](http://csrc.nist.gov/publications/nistpubs/800-57/sp800-57_part1_rev3_general.pdf) §5.6.1 p.62–64 specifies a correspondence between RSA modulus size $n$ and expected security strength $s$ in bits:
Strength RSA modulus size
80 1024
112 2048
128 3072
... |
I'm studying about preimage resistance property of the hash functions.
In particularly I'm reading as the missing of this property can be fatal in digital signatures that use RSA.
Further details:
Let e be the public exponent , d the public one and n the modulus.
Let be C the attacker.
C could compute:
... |
I see three kinds of weaknesses here. The need for padding is not an implementation weakness but an algorithmic weakness. RSA is not an encryption algorithm nor a signature algorithm; [RSA-OAEP](http://en.wikipedia.org/wiki/Optimal_asymmetric_encryption_padding) and [RSA-PSS](http://en.wikipedia.org/wiki/PKCS1#Schemes)... |
I'm studying about preimage resistance property of the hash functions.
In particularly I'm reading as the missing of this property can be fatal in digital signatures that use RSA.
Further details:
Let e be the public exponent , d the public one and n the modulus.
Let be C the attacker.
C could compute:
... |
I'm studying about preimage resistance property of the hash functions.
In particularly I'm reading as the missing of this property can be fatal in digital signatures that use RSA.
Further details:
Let e be the public exponent , d the public one and n the modulus.
Let be C the attacker.
C could compute:
... |
Suppose one has a (strong) shared secret key and wishes to authenticate a very long string in a way that will allow the verifier to verify small substrings without reading much of the stored data and without much storage overhead.
The trivial way to do this is to have a nonce, divide the string into chunks, MAC eac... |
I'm studying about preimage resistance property of the hash functions.
In particularly I'm reading as the missing of this property can be fatal in digital signatures that use RSA.
Further details:
Let $e$ be the public exponent, $d$ the private exponent and $n$ the modulus.
Let be C the attacker.
C could c... |
**Background:**
I'm making a program for fun as a learning exercise. I want to generate some random key material. For my program is just for encrypting/decrypting plain text letter by letter so I've chosen to use the [ASCII printable character set][1] (what characters you can type on a standard US keyboard) which gi... |
Algorithm: How to use x and y mouse movement co-ordinates to generate random data? |
**Background:**
I'm making a program for fun as a learning exercise. I want to generate some *actual random* key material (not pseudorandom). For my program is just for encrypting/decrypting plain text letter by letter so I've chosen to use the [ASCII printable character set][1] (what characters you can type on a st... |
I studied some encryption and decryption and I have found some very interesting problem to solve on the internet. I hope I am writing to right site - there are so many in StackExchange otherwise I hope some moderator will move it.
So, how to choose the appropriate public lets say (i, m) and private (j, m) kies which... |
How to choose the appropriate public (i, m) and private (j, m) kies? |
I studied some encryption and decryption and I have found some very interesting problem to solve on the internet. I hope I am writing to right site - there are so many in StackExchange otherwise I hope some moderator will move it.
So, how to choose the appropriate public lets say (i, m) and private (j, m) keys which... |
How to choose the appropriate public (i, m) and private (j, m) keys? |
Is it possible to pre-choose a private RSA key, then obtain a public key from it?
|
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