instruction stringlengths 32 27.2k |
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(Disclaimer: I am regular software engineer with only basic crypto knowledge, so helpful if can be explained for a layman.)
I am concerned about generating weak keys on a shared linux box with openssl. Some questions:
How low does entropy have to be for it to be dangerous? If I run cat /proc/sys/kernel/random/entrop... |
How random is the value $ZZ$ in the DH protocol?
This question was triggered by this somewhat naïve implementation in I2P shown by Sergei at Stackoverflow. Obviously $ZZ$ is distinguishable from a random oracle, as the first byte will be lower or equal to the highest byte of $p$, if $p$ is encoded using the same $I2O$ ... |
What is the difference of the CDH problem in different groups? In particular, given a group $\mathbb{G}_1$ of order $q$ that is a subgroup of $\mathbb{Z}_q^*$, $q$ prime, and another group $\mathbb{G}_2$ of order $p$ that is a subgroup of $\mathbb{Z}_p^*$, $p = 2^n$, is solving the discrete log problem easier or harder... |
Are there hash functions that make use of pseudorandom functions. Precisely, I'm looking for a specification of a hash function based on PRF (and based on the security of such a primitive).
|
We have a h/w accelerator in our SoC and it can do sha256. The restrictions are it's input descriptors (which defines the input packet and len) must not straddle 64K boundary. When it does we can split the descriptors into two. However the total number of descriptors can be max of 64. This means 64K * 64 = 4MB seems to... |
I am from a web development background (I don't know an awful lot about cryptography or how the algorithms themselves work), so I am asking this question in simple terms.
Consider a hash of the word 'test' using SHA1:
a94a8fe5ccb19ba61c4c0873d391e987982fbbd3
If I were to use SHA512 instead and then simply take the fir... |
It has recently emerged that a paper that was scheduled to appear at Usenix Security 2013, titled "Dismantling Megamos Crypto: Wirelessly Lockpicking a Vehicle Immobiliser", has been censored according to a newspaper article in the "Guardian".
A court in the UK issued a temporary injunction barring the scientists from... |
I grasp that having known plaintext encrypted with the public key doesn't provide a means of discovering the private key (that being the whole point...).
But if one were in a situation where they didn't have access to the private key, but did have access to decryption by the private key, would the actual key be vulnera... |
Following on from here, I am unconvinced that encrypting twice with RSA is a waste of time: doesn't it depend on what is placed in-between the two encryptions?. What would happen if a permutation was applied at this point? How strong will the encryption be then?
That is,
$$f(m^{e_1}\mod n_1)^{e_2} \mod n_2$$
I am not 1... |
I am trying to find attacks on a theoretical protocol or prove its security. An initiator wants to establish a shared key with a responder with help of a trusted server.
We have the following roles: $I$: Initiator, $R$: Responder, $S$: Server.
There are long-term symmetric keys between all pairs of involved entities de... |
I have just learned about using PGP/GPG for email encryption and one thing bugs me:
How is it possible that a message encrypted with somebody's public key can be decrypted only with that person's private key?
This concept of asymmetric encryption is not easy for me to understand. Simply said, I would expect that the pr... |
I am just learning about the GCM mode of AES and I'd like to start using it in my software. However, I have a question about its use. As I understand it the output of a GCM encryption operation is the ciphertext plus an "authentication tag." I know that the key needs to be guarded from discovery, but does this authe... |
Assuming in the future there was a functioning 1024 qubit quantum supercomputer and it could run Shor's algorithm or Grover's algorithm to crack encryption very quickly. I'm interested in how the number of qubits translates to performance improvement over a regular 2 bit computer.
For example, if I used Shor's algorith... |
Given a server that broadcasts all received data to all connected peers (except the sender), two participants can have an encrypted conversation using a self-synchronizing method like CFB and some error detection.
How secure is this given that anyone can not only listen but also paste in chosen text into the stream? Is... |
Every time when I read a paper that has digital signature, when it comes to prove the security of a digital signature scheme, many chances that the author will use the forking lemma.
The forking lemma says as follows:
Let $\mathcal A$ be a probabilistic polynomial time turing machine, given only the public data as inp... |
I came across this article, which describes a method, developed by UCLA CS professor Amit Sahai et al, for using functional encryption in order to achieve software obfuscation. The paper that the article refers to is available here. Has anyone digested the paper and have more information to share? Are the results as gr... |
Question:
A stream of cipher operates on a data stream of 6-bit characters using a simple mono-alphabetic substitution technique. Estimate and explain the number of different substitution alphabets possible. The key is effectively the substitution alphabet, which can be expressed as a $384$-bit number (i.e. $64×6$ b... |
What is known about the security of identity-based encryption schemes against attacks that involve seeing multiple ciphertexts and then receiving the private keys corresponding to some of those ciphertexts?
For example, is it known that feasible adversaries will have a negligible (in the security parameter $k$) probabi... |
Users in my system will be given a device that contains a 128-bit AES user key. The user key will be derived from 64 bits of public data related to the user, which is unique but very predictable (i.e. a sequential user ID value). The value of the user key must be kept secret from the users. I assume users are fully awa... |
As I understand, if two users have a shared key, it is possible to encrypt a message using symmetric key encryption.
So when a secret key is shared through Diffie-Hellman asymmetric key exchange, it means that the users have their shared key. So why can't AES keys be generated from shared keys, and why not use only AE... |
I have two systems which need to encrypt their communication by AES-128. The key for the AES encryption should be exchanged with the Diffie-Hellman (DH) algorithm.
Now, I've read about DH and got a lot of question marks over my head. These are my questions:
Typically with AES-128, you need a password and a key which w... |
Homomorphic encryption schemes are PKE schemes with an additional special method Evaluate.
The Evaluate method takes input any function (as boolean circuit) and encrypted inputs of the function and evaluates the circuit. The results of such function are still encrypted under the public key $PK$.
Now, if the user needs... |
On page 14 of "Keccak and the SHA-3 Standardization" (February 6, 2013) it says:
Instantiation of a sponge function
the permutation KECCAK-f
7 permutations: b → {25,50,100,200,400,800,1600}
Security-speed trade-offs using the same permutation, e.g.,
SHA-3 instance: r = 1088 and c = 512
permutation width: 1600
s... |
As we can know that the best two-pass AKE protocols with DH message can achieve is the weak form of perfect forward security (wPFS) which guarantees security against the passive adversary. But "Strongly Secure One Round Authenticated Key Exchange Protocol with Perfect Forward Security" (Hai Huang) claims that the AKE i... |
Homomorphic encryption schemes are PKE schemes with an additional special method Evaluate. Evaluate method takes input any function (as boolean circuit) and encrypted inputs of the function and evaluates the circuit. The results of such function are still encrypted under the public key PK.
Sometimes, it would be too wi... |
I was reading this article and had a question....
http://arstechnica.com/security/2013/08/gone-in-30-seconds-new-attack-plucks-secrets-from-https-protected-pages/
As I understand it TLS/SSL work in such a way that even the Requested URL is encrypted. So, my question is...would it be possible to create an SSL proxy tha... |
Assume an ElGamal Cryptosystem. Assume a set of three players, $P_1$, $P_2$ and $P_3$. The private key $x$ is shared among the players. The player $P_1$ has a piece of the private key $x_1$, $P_2$ has the piece $x_2$ and $P_3$ has $x_3$.
Assume the following messages, $m_1$ and $m_2$.
Let $E(m_1)$ and $E(m_2)$ be two E... |
In the zero knowledge proof using QR, why do we even bother with the server sending us $b = 0$ back? As I understand it, the server selects $b = 0$ or $b = 1$. If $b = 0$, then the client (Alice) generates a random number $r$ and sends back $r^2 \bmod x$, while if $b = 1$, then Alice sends back $r^2 \, y \bmod x$. How ... |
Quoting "Verified Security of Redundancy-Free Encryption
from Rabin and RSA", Chapter 2 (on page 4):
OAEP was proved IND-CCA-secure by Fujisaki et al. [28] under the assumption that the underlying trapdoor permutation is partial-domain one-way. This is in general a stronger assumption than just one-wayness, but fortun... |
I understand that:
$$x_{montgomery} = \frac{1 + y_{edwards}}{1 - y_{edwards}}$$
Using the libsodium ed25519 implementation, I have tried to write the following:
void keypair_2(unsigned char *pk, unsigned char *sk)
{
ge_p3 A;
int i;
sk[0] &= 248;
sk[31] &= 63;
sk[31] |= 64;
ge_scalarmult_base(&... |
Block ciphers have modes like GCM or OCB that combine primitives to provide both authentication and encryption.
Are there similar constructs for stream ciphers, which provide both authentication and encryption using only one cryptographic primitive - actual stream cipher (or keystream)?
|
I'm not realy experienced with programming and such but I am wondering if the following could be implemented in, lets say, python
we have the following ciphertext sequence
AO AP AL EE IL OP QR IV OD DD GH DK OL FK PO AD GG PO FK OL DK GH OL OT RI DH SK
and I know part of the plaintext says:
risetovotesir
Than for su... |
At Blackhat 2013 this week, there was a talk saying RSA is (essentially) doomed in the near future.
networkworld.com ~ “Black Hat: Elliptic curve cryptography coming as smarter algorithms threaten RSA”
What "two devastating attacks in the past 6 months" is Mr Ritter referring to, and how real is the threat to RSA?
|
Given a TOTALLY HYPOTHETICAL scenario in which passwords for over a million accounts in over 200 databases have been stored using 3DES, a key derived from a (single) MD5 hash of a customer-controlled (rarely changed from the default) pass-phrase, a hard-coded IV (same for every account in every database), and a cipherm... |
This question is related to this one in intention, and this one in scope.
Would I be guarding myself against future attacks on a single PRNG if I combine two (or more) together?
I am thinking of using the Fortuna PRNG together with AES in counter mode, each initialised by a different source of entropy (now exactly what... |
RSA and ElGamal can be implemented using the technique of Elliptic curves. I am confused on why the it seems that Elliptic curves are not so popular in cryptographic applications since they provide the same security with smaller key sizes?
|
In mix Columns we have:
$$C(x) = \{03\}X^3 + \{01\}X^2 + \{01\}X^1 + \{02\}$$
In Viktor Fischer's Paper on MixColumn and InvMixColumn Resource Sharing, in page 2, Equation 8, it's been said that $C^2(X)$ can be computed as follows:
$$C^2(x) = \{04\}X^2 + \{05\}$$
Can anybody explain why is that?
|
I am interested in the theoretical consideration of the bit strength of an encryption key and its precursor.
Assume a given environment as follows:
a. My encryption algorithm is AES-256
b. My key derivation function is PBKDF2 with HMAC-SHA1 with
b1. Salt strength of 128 bit (32 chars of a truely random hex string)
... |
Since 18th of December 2010 Germany makes use of an identity card that should allow electronic authentication:
(image source: commons.wikipedia.org)
From a users perspective, the authentication seems to work as follows:
A program requests permission to read information (name, birth date and place, address, photo, se... |
In AES algorithm, in the key schedule,
Why does the expansion of a 256 bit key need an extra application of the S-box, unlike the expansion of 128 bit and 192 bit keys ?
(The obvious answer would be "because it is more secure" ... but why ? And if it is more secure, why don't use it on 128 and 192 ?)
|
There is a paper from Peter W. Shor from 1994: Algorithms for Quantum Computation: Discrete Logarithms and Factoring, and I have a question about it and the algorithms presented.
For integer factoring problem, Shor's algorithm is working as a fast period finder for function f(x) = a^x mod N, where semiprime N is equal... |
Every time a file on the data partition is created, Data Protection creates a new 256-bit
key (the “per-file” key) and gives it to the hardware AES engine, which uses the key to
encrypt the file as it is written to flash memory using AES CBC mode. The initialization
vector (IV) is the output of a linear feedback... |
In 2012 a group of researchers collected a large amount of RSA moduli and calculated their greatest common divisor in order to find common factors between them. By finding a common factor they could the divide and completely factorize the key. They concluded that the vulnerable moduli where generated by PRNGs with inad... |
I have an elliptic curve defined over finite field where $S_1=aP$ . Is it valid to say that $S_1P$ can also be computed. $P$ is the generator of the group.
What my real question is that. Should '$a$' be always an integer or can it be a group element itself??
|
I am a bit confused on the hardness of the discrete logarithm problem. Does it become intractale only when it is mod n, where n is a large composite number (Like RSA key). What about if it is mod a prime number p? what is the complexity and method for solving it? Can we reduce the problem of integer factorization to d... |
In Section 7.2 "Validation of HOTP Values" of the HOTP spec (RFC 4226) it says, in part,
The HOTP client (hardware or software token) increments its counter
and then calculates the next HOTP value HOTP client. If the value
received by the authentication server matches the value calculated by
the client, then the HOTP... |
What is the exact difference between the CKM_RSA_PKCS and CKM_RSA_X_509 mechanisms in the PKCS#11 v2.20 specification (Please explain with an example)?
|
Would something like the following improve security (against rainbow attacks, not brute force)? Assume that $P$ is a user-chosen password, and the objective is to obtain a hash $H$ for password checking.
Let $S$ be a random salt.
Let $A_1 = MD5(P || S)$
Let $A_2 = MD5(A_1 || P) || A_1$
Let $H = MD5(A_2)$.
The idea is... |
A system is used to securely store account numbers.
When an account number is added to the system it is securely encrypted and stored in a database along with the IV and a reference to the encrypted record is returned (so that the encrypted record can be retrieved at a later date).
If a second request for an identical... |
I was wondering if changing the cipher mode to AES-XTS in EncFS would be a sound idea. EncFS uses AES in CBC mode until the last 1KB block, and CFB mode for the last block if len(block) < 1KB. This ensures that len(plaintext) == len(ciphertext).
The design seems somewhat convoluted, but understandable considering thos... |
I have an application where I want to be able to send an encrypted file, and then mete out "keys" that allow the receipient to decrypt the file from a certain point to the end of the file. Actually, it's from a certain point to the beginning, and I'm doing the above by reversing the file.
Looking at AES (and thus Rijan... |
Simple version:
Create software that takes a database of the dictionary, alphabet, and phrases. Randomly generate a database of random strings of letters/numbers/symbols of varying length. Randomly assign different strings to different words/letters/phrases.
Frequency analysis should already be hard because you're ope... |
As I understand it, the less people know about the internals of my protocol or cipher, the more secure the protocol is. However Kerckhoffs's principle states that
A cryptosystem should be secure even if everything about the system, except the key, is public knowledge.
To be more precise, it's the 2nd principle that s... |
I'm writing a client application that wants to store some secret information with a storage service. The client has to authenticate the user with the service and the service should not be able to decode the information that it stores for the user. Authentication against the service has to be based on username - passwor... |
I was thinking of a potential new way to increase someone's account security.
The idea was allowing the user to choose one of the hash formulas available in the software (example: "MD5", "SHA512" and "Whirlpool"), decreasing the chances of any intruder to find out the hashing system used in case passwords are — for som... |
I have a time authority and I want to securely set a client's time to this authority's time/date within a precision of $\delta$ seconds. The authority's public key is known to the client. This was my idea:
A client sends a request with a 128-bit randomly generated nonce to the authority, and starts a timer.
The server... |
I've been reading about SHA-1. I read that SHA-1 is insecure as it uses the Merkle-Damgård construction and the Merkle-Damgård construction is — according to Wikipedia — susceptible to a variety of attacks. However, I have not been able to come up with a single example of how these work.
Can someone give me an example... |
As without using modes we can also encrypt and decrypt data then what is the need of using modes in DES?
|
If an attacker were able to get a hold of 2 encrypted messages that were both encrypted in a one time pad with a password that were each similar but had one change in the first character, could it still be cracked?
Let's say my first set of data was encrypted with "1password" and my second set of data was encrypted wit... |
I am a beginning programmer interested in coding an application of my own to encrypt sensitive files of mine. For example: lists of passwords, bank accounts, Credit Card numbers etc.
I was wondering what would be the easiest encryption algorithms to learn from a purely theoretical point of view?
|
I am encrypting a string in a format like this:
Byte 1: 1 (this byte is CONSTANT and KNOWN)
Byte 2-18: a random string of characters that is never the same.
Byte 18-34: unknown number that is sequentially incremented each time
(it's a primary key from a mySQL AUTOINCREMENT column)
The entire 34 bytes is e... |
Alice has a bank account number, but has forgotten which bank it is for. There are 4 banks, run by Bob, Carlos, David, and Eve.
She could find out by going to all of the banks and asking if they have the account number. However, if Eve learns Alice's account number, then Eve will go to Alice's actual bank and steal all... |
I'm trying to design a deterministic encryption scheme to enable searching in untrusted databases with the smallest possible IV overhead on ciphertexts. I know it's very bad practice but unfortunately it's a business requirement, so I'm just trying to offer the best security I can under the circumstances.
Right now I'... |
Would a scheme like the following work to allow authentication of a sender:
A nonce is appended to data, and the result is encrypted. The encrypted pack is sent to the other party. The sender then contacts the receiver through an authenticated channel (or one that is sufficiently good for the current purposes) and prov... |
This note (http://maths-people.anu.edu.au/~brent/pd/primality4.pdf) states that AKS is not practical. However, it is known that AKS runs in polynomial-time, and I cannot understand where the slowness of AKS algorithm comes from? Brent, on the above link, justifies this to the high probability of hardware errors during ... |
I'm using AES-256-GCM for authenticated encryption. In order to decrypt, the ruby OpenSSL library requires an auth_tag parameter (in addition to the key and iv). This, according to the ruby docs, is because authenticated encryption is only supported with associated data (AEAD).
How can I use this auth_tag to decrypt? T... |
In a comment to an answer I wrote to another question, CodesInChaos wrote that:
"Problem with SRP is that an attacker who impersonates a server learns the password hash, enabling offline search."
and further that:
"If the server successfully impersonates a legitimate server [...] they learn the public key of the cli... |
I'm trying to figure out a way to do public key encryption on a very large piece of data.
For this, I of course want one side to do the encrypting but is unable to decrypt the data, and the other side to be able to decrypt data.
But for RSA encryption, there's a limit to the reasonable size-performance on how big it ca... |
The Koblitz elliptic curves specified in the SEC2 document https://docs.google.com/viewer?url=http%3A%2F%2Fwww.secg.org%2Fcollateral%2Fsec2_final.pdf all have the nice feature that the parameters are highly non-arbitrary; the modulus is simply a few powers of two put together, and the a and b parameters are 0 and 7. Th... |
Definition
E: AES encryption
D: AES decryption
x: plain text
y: encrypted text
k: key
In original AES cipher,
encryption: y = E(x, k)
decryption: x = D(y, k)
Then I define the "reverse AES cipher" as below.
encryption: y = D(x, k)
decryption: x = E(y, k)
Is "reverse AES cipher" safe as original AES?
or, is saf... |
If DES decryption is the same as encryption done in reverse order, then how can the reversed S-Box convert 4 bits into 6 bits?
|
I'm building an embedded device that I plan on distributing. Periodically the device will poll my server to check for updates and commands. I'd like the device to verify that any messages(JSON strings parsed by a client written in Go) and updates are actually from me.
My plan is to use use Go's crypto/ecdsa library to ... |
Why does DES use exactly 16 rounds and not more or less than 16? What is the significance of using 16 rounds?
|
How does certificate-based encryption solve key revocation problem?
For example, if a user accidentally reveals its secret key or an attacker compromises it, the user may request revocation of its certificate. Alternatively, the user's company may request revocation if the user leaves the company or changes position an... |
While reading the Wiki page on RC4 I noticed that the key size must be in the range of 40–2,048 bits. So should I understand like this, that I can have a key that has length of, lets say 333 bits? (any decimal number between 40-2048?) How about inputs length?
Imagine that I can ask a user to give me an input length (fo... |
I am encrypting files for storage in an untrusted location, using a custom Java program to do that. There is only one user, but there are many files.
I am using AES in CBC mode with PKCS5 padding, and the key is created from a single passphrase using PBKDF2.
Question: Would it increase security if I used a different sa... |
Are there any cryptographic hash functions for which there is a known pre-image attack, or a known second pre-image attack, but not both?
The attack doesn't have to be practical - just anything that beats the security claim of the hash function.
Intuitively, 2nd pre-image attacks would be easier to find than pre-image ... |
I am studying Fractal Merkle Tree Traversal algorithm in the book “Post Quantum Cryptography” (PDF). On the [pag. 54] I don't understand this paragraph:
We may determine the number of pebbles returned at these times by observing that a leaf is returned every single round, a pebble at height
$ih + 1$ every two ro... |
I was reading How is CipherCloud doing homomorphic encryption? and was wondering:
Is there a technically feasible way for companies like CipherCloud to use homomorphic encryption (HE) while preserving full functionality in a third party SaaS app (e.g. Salesforce)? Furthermore, can it be done without requiring that the ... |
Reports are surfacing that Android's Java SecureRandom class has issues and isn't totally secure.
A specific example of how this issue translates to applications is bitcoin, where reports are stating that the bitcoin wallet is at risk of theft. With bitcoin specifically, the reports say that "colliding R values" can re... |
Most of the libraries I've seen allow you to add encrypted numbers. Is it possible to subtract and multiply them?
|
Is there any problem with using social media (i.e. Facebook) as a directory of public keys?
For example, couldn't Alice put a note containing $(g^a \bmod p, g, p)$ on her Facebook page so she could receive email attachments which have been encrypted with the common secret value?
That is, Bob would encrypt his message w... |
This is how the Pedersen commitment seems to work:
Let $p$ and $q$ be large primes such that $q \mid (p-1)$, let $g$ be a generator of the order-$q$ subgroup of $Z_p^{\star}$. Let $a$ be a random secret from $Z_q$, and $h=g^a \bmod p$.
The values $p$, $q$, $g$ and $h$ are public, while $a$ is secret.
To commit to a mes... |
Right now I'm using a simple padding system that takes the plaintext, hashes it with SHA512, and appends $x$ bytes of the hash as padding where $x$ is the delta between the plaintext and nearest blocksize multiple.
Is this considered a secure method of padding the message? I am also authenticating the encrypted data us... |
I know it's a highly theoretical topic, but I was wondering if there was any research out there about what cryptography would be like assuming that we had access to nondeterministic Turing machines.
It seems to me like you couldn't have the kind of exponential hardness assumptions that we currently have, but the Time... |
I read a wiki page about Camellia cipher and know that it is a block cipher that can use 128-bit, 192-bit or 256-bit keys. But I cant find any information about if its a symmetric cipher (uses one key for both encryption and decryption) or asymmetric cipher (uses different key for encryption and different key for decry... |
From what I've been reading, Keccak's round function is reversible. That's pretty obvious for the $\rho$, $\pi$ and $\iota$ transforms. For $\chi$ to be reversible, $x$'s range has to be odd — but that's alright since Keccak's $x$ has a range of 5. Yet, what criteria make the theta step reversible?
Checking some small ... |
What I am picturing is something like this:
Block A: "Hello, how are you today?"
Block B: "The weather reminds me of summer."
I encode this, giving me two keys and a resulting encrypted block e.g.
AP: 2da93742a7340ad12372aff
BP: 023cd97d40293d7c4027947
DATA: ksdjhfksdjhf0wddfg74059r7sdhdkfh
Whereas decrypting with AP ... |
Let's say that Alice and Bob complete a key exchange and then Alice uses that key k1 to encrypt a 256-bit key kaes1 and sends it to Bob. From there, Alice and Bob exchange a lot of messages back and forth, using AES-256 to symmetrically encrypt the data with the key kaes1.
Then, Charlie comes along and wants to partici... |
What security flaw exists (if any) in the solution of this non-encrypted authentication scenario?
An unencrypted message passes one-way from computer A to B. Its transmission is viewable by the public. The message does not need to be kept secret. Both A & B have already securely exchanged any needed keys. A and B keep ... |
The Schnorr protocol is a 3-steps proof of knowledge of a discrete logarithm, whose interactive version works as follows.
Let $p$ and $q$ be two public primes, such that $q \mid (p-1)$, and let $G$ be a cyclic subgroup of $\mathbb Z^\times_p$ of order $q$ (i.e. a Schnorr group) with generator $g$. The prover $P$ wants... |
A friend shared with me the following link: Encryption is less secure than we thought
I'm not a security expert and could understand great part the article, except the section about noise, but what I haven't figured out is the impact of that research in real life.
What does it mean for mortals, in practice?
|
I have a ciphertext encoded with One Time Pad. I do not know the key. How can I find the possible keys which when decoded, will result in a meaningful plain text?
|
I am about to go study for my masters in machine learning, data mining and high performance computing, but have recently become very interested in cryptography after taking Dan Boneh's Cryptography course on coursera.com.
I was wondering if there are any practical applications for machine learning in cryptography? A q... |
Does there exist a voting scheme where voters cast private encrypted votes that automatically become public only after the threshold number of votes is cast?
It needs to be done without a central authority that is trusted to hold keys. I don't need it to be receipt-free, I just want it to be authority free and automati... |
I am trying to look into a relation between the following three problems which are widely used to build public crypto systems:
Integer Discrete log
Elliptic Curve Discrete log
Integer Factorization
Can any of these problems be reduced to another such that an efficient solution to one of them yields an efficient solut... |
I am looking for a cryptographic hash function that can be computed by a human using only paper and pen without ever leaking any information about the plaintext on the paper.
The cryptographic hash function should be computable by an algorithm satisfying the following properties:
Input/output: Any input/output set is ... |
A “meet-in-the-middle” (not “man-in-the-middle”!) attack on textbook-RSA was presented to me. The only requirements for it was that the attacker gets the output of RSA and the public key, and that the message be the product of 2 numbers of the same magnitude, which apparently happens with 20% probability. (ie: only eav... |
I was checking the RFC's after wondering for some time. In RFC 4226 - HOTP: An HMAC-Based One-Time Password Algorithm, it states on the appendix:
A simple enhancement in terms of security would be to extract more
digits from the HMAC-SHA-1 value.
For instance, calculating the HOTP value modulo 10^8 to build an 8-
digi... |
Suppose one has an ideal block cipher
$E \: : \: \{0,\hspace{-0.04 in}1\hspace{-0.03 in}\}^k \times \{0,\hspace{-0.04 in}1\hspace{-0.03 in}\}^w \: \to \: \{0,\hspace{-0.04 in}1\hspace{-0.03 in}\}^w \;\;\;$ and $\;\;\; D \: : \: \{0,\hspace{-0.04 in}1\hspace{-0.03 in}\}^k \times \{0,\hspace{-0.04 in}1\hspace{-0.03 in}\}... |
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