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Let $f$ = $\{f_k\}$ be a pseudorandom function family.
Let $G(x)$ be a pseudo-random generator such that:
$G(x) = f_x(0^k)f_x(1^k)$ where $k=|x|$.
I don't understand the meaning of $1^n$ and $0^n$, and the differences between them, in that context.
What do they represent?
What is the special role / effect they have ... |
While reading Attribute Based Encryption Schemes, I did not quite understand what a monotonic access structure or non monotonic access structures are.
Is there a popular explanation of those terms ? any references ?
|
The Linux kernel supports symmetric and asymmetric hash functions. E.g. sha1, sha256, ...
See tcrypt.c and search for test_hash_speed and test_ahash_speed.
I know what the difference is between symmetric and asymmetric ciphers, where the encryption and decryption key is not the same.
Question
What is the difference bet... |
I know that a simple monoalphabetic substitution cipher is considered extremely weak, on account of linguistic frequency-analysis attacks. However, assume the following:
cleartext is encrypted (with 256-bit AES, for example), and the resulting cipher is in base64 format
the client has a key of 64 chars (a-z, A-Z, "+/... |
Is there any library/tool available which can allow me to search over encrypted data?
I would like to encrypt data on client side, send it to cloud and perform search in cloud.
I've been reading about homomorphic encryption and though there is CryptDb available which makes it possible to run encrypted DB in cloud, bu... |
I saw a sample code where the same password is salted with a different value (using PBKDF2) for each encryption. That means that the salt must be stored for each encrypted message.
I don't understand why they do that since AES is used here in CBC mode with a random IV at each encryption, so a same plaintext will not pr... |
I have a string "abcd pqrs". This string is digitally signed with an X.509 certificate (with its private key) and it produces a signature.
From the signed string, is it possible to find out what hashing algorithm was used?
Also, does the signed data always contain the certificate or the public key used to sign the dat... |
I've been struggling on this problem for a while now : the Hill cipher is well-known to be vulnerable to known-plaintext attack due to its linearity. Given a key matrix $K$ of size $n\times n$, one can retrieve the key with as little as $n^2$ plaintext/cipher text couples.
All examples found on the Internet assume an a... |
Okay here are my requirements.
I need a solution that can do the following.
Lets say I have an encrypted piece of text with the value "20".
and I have UserA and UserB
I give UserA the Keys (/5 and /2), meaning divide by 5 and divide by 2.
I give UserB the Key (/10 and /1) meaning divide by 10 and divide by 1.
using bot... |
I would like someone to explain me how to generate DES subkeys, because in the documentation that I saw, sometimes they say:
"We rotate the initial key according to the number of iterations given by this sequence:
1, 2, 4, 6, 8, 10, 12, 14, 15, 17, 19, 21, 23, 25, 27, 28."
and sometimes they say:
"The two halves... |
I'm taking a course in cryptography, and I would value any comments. This is not too technical a question, but more about directions or strategy in cryptography. My question is, is public key cryptography, for instance, "just" a question of the difficulty of dealing with large integers? I can understand that factoring ... |
Common Criteria classifies the requirements for true Random Number Generators, and specifies how these should be tested against failures (these can occur accidentally, or following deliberate attack, e.g. by very low temperature). The relevant Application note and Interpretation of the Scheme is AIS 31 version 3.0 (in ... |
When given $p = 5, q = 11, N = 55$ and $e = 17$, I'm trying to compute the RSA private key $d$.
I can calculate $\varphi(N) = 40$, but my lecturer then says to use the extended Euclidean algorithm to compute $d$. That's where I get stuck.
Here's my work so far:
First I use the Euclid algorithm to calculate:
40 = 2(17)... |
In asymmetric ciphers we publish the public key for anyone, which means an attacker can encrypt any message they want and compare the ciphertext and plaintext without communicating with the owner of the private key. So do known-plaintext attacks make sense for asymmetric ciphers, or are they only for symmetric ciphers?... |
Throughout the literature, it is stated that EC cryptosystems outperform RSA and Discrete logarithm cryptosystems, but I cannot understand how ECC would be more efficient than RSA and DL in terms of computation and storage.
Is there any pragmatic performance analysis comparing these cryptosystems so that I can underst... |
I am using HMAC (hmac-sha256 to be precise) message authentication without encryption. My question is, is having a short message make it easy to determine what my secret key is?
My C# code is as follows
HMACSHA256 hmacSha256 = new HMACSHA256(new byte[]{0xfa, 0x35, 0x24, ..., 0x5e}); // 64 byte secret key
byte[] authF... |
I have read up on rainbow tables and think I understand the idea behind them. However, I find that it would be better for me to actually attempt to implement a (very basic) rainbow table generator in order to get a proper feel to using rainbow tables.
However, I face the problem of there not being descriptions on how t... |
We know that Grover's algorithm can speed up cracking symmetric keys. Basically the keyspace is halved. This means we have to use at least a 256-bit key (to get 128-bit security).
I heard somewhere it also has an effect on the block size (so we should use 256-bit blocks instead of 128)!
Is that true?
|
Possible Duplicate:
Why is h(m||k) insecure?
Length-extension allows to append any data to the message while not knowing the secret. Any length-extension explaination one the web considers the situation when the secret is prefixed to the data, but is this attack applicable to the situations when the secret is append... |
What properties should an ideal straight P-Box exhibit?
|
Obviously, much of cryptography requires the assumption that adversaries have bounded computing power.
So, I was wondering, are there any fields in cryptographic research for which high power computing would aid researchers? Obviously, even the most advanced computers today will not give them an asymptotic advantage, ... |
I am doing a course on cryptography on coursera and one of the topics covered was the ElGamal Encryption system.
I am using the terms as defined in Wikipedia.
Alice publishes $g$ and $g^x$. Theoretically an attacker could calculate $g^i$ for all $i$ from 0 to $n$. At some point the attacker will get the value which is... |
Sponge hashes like Keccak(SHA-3) and CubeHash, xor a message block into part of the internal state. Why use a reversible operation like xor for that, instead of replacing that part of the state with the message block?
It clearly has no effect on pre-image and collision resistance. It's trivial to transform collisions/... |
Let $E_k$ : {0,1}$^l$ be a block cipher encryption function with block-size $l$ and key-length $n$.
In class, we saw that a double encryption with two independent keys $E{}'_{k_1k_2}(x)$ = $E_{k_1}(E_{k_2}(x))$,
can be brute-forced in $O(2^n)$ time and $O((l + n)2^n)$ space using the meet-in-the-middle attack:
creat... |
I'm looking for a simple way to perform homomorphic crypto on 32-bit integers. My only requirement is that I can add and subtract from the plaintext value without actually decrypting it. The crypto need not be particularly strong - the implementation is designed to be a deterrent rather than something more concrete.
Ar... |
I have noticed that some programs used for file encryption will tell you if an entered key is wrong when you try to decrypt. It seems (to me at least) that this would mean that the key somehow is written into the encrypted file. And the algorithms that I know of will produce an output even if the key is wrong.
How doe... |
I made a cool 5 word passphrase back then using the old Diceware method and use it as a master password. The question is as computing power increases will we need to add more and more words to our passphrases which we will eventually forget? I'm in my mid 30s, will passphrases be enough in my lifetime? :) So back then,... |
Is there a reason, why in pre-shared key mode, Wi-Fi session key is not secured with something like Diffie-Hellman but instead is derived from PSK key and some information exchanged in clear during sign-on?
|
I am currently looking at the security of cryto USB drives for storing x509 certificates. I have one in possession currently. It can be read/written to using the Microsoft Crypto APIs. Anytime one reads/writes to/from the device it prompts for a PIN. The PIN can be changed using a UI which installs with the device.
I w... |
Basically my knowledge in passwords consist of setting up a Diceware master password back then, and I know hashes are not convertible back to the original password.
Some basic question I want to know the answer for is how can a password be predicted from the hash? Like it can be known how many characters long it is exa... |
Possible Duplicate:
Using CBC with fixed IV
Forgive me if this has been asked before, I looked but haven't seen any answers that suit.
Is there any danger in using CBC, encrypting a message plus one initial block of garbage, discarding the IV, and when decrypting, use any random IV, and then discard the resulting in... |
Rather, is it possible for big prime numbers?
Classroom examples usually involve smaller primes, so for example if you are given a prime number pair $p = 3$, $q = 13$ you would get $n = 39$ and $e = d = 5$, making encryption and decryption the same for a message $x$ or ciphertext $x$.
This can be a big problem, e.g. if... |
My friend and I have been generating a few SSH2 RSA keys and noticed all the public keys begin with AAAAB3NzaC1yc, with the similarity extending to AAAAB3NzaC1yc2EAAAABIwAAAQEA between two keys generated on the same machine in two successive attempts (googling AAAAB3Nz ends up getting a few hits as well).
Is this norma... |
I'm wondering why RSA encryption usually is only used for messages that fit into one block.
For larger messages hybrid encryption in combination with symmetric ciphers like AES seem to be the solution of choice e.g. c.f.
Bouncy castle FAQ.
I know about the advantages of hybrid encryption considering
better performance... |
What does "blinding" mean in cryptography, and where do we usually use it? Can you describe a sample implementation?
|
I have made a study on digital signatures, especially on the Schnorr digital signature, and I was just wondering if there is some way I can find names of actual (known) applications that have applied and used this kind of digital signature.
I haven't been able to find anything by myself, so any help is appreciated.
|
Let $p$ be a prime number, and let $g_{1},g_{2},...,g_{n}$ be $n$ generator of $Z^{*}_{p}$. We have a list $y_{1},y_{2},\dotsc,y_{n}$ of elements in $Z^{*}_{p}$ such that for every $i\in \lbrace1,2,\dotsc,n \rbrace$ we have $y_{i}=g_{i}^{x_{i}} \bmod p$ for some number $x_{i}$ (but we don't know $x_{i}$). I am trying ... |
Can the knapsack be used in cryptography in a secure sense (described below)?
Knapsack problem: Given some number $X$ and a set $W$ of weights $w_1, w_2, ... w_n$, find a subset $S$ of $W$ (if it exists) whose weights sum to $X$.
Even though this problem is NP hard, there exist "pseudo-polynomial-time" algorithms for ... |
Can we use a threshold scheme to construct a (yes/no)-election protocol, such that every voter can give a positive or negative vote or he can abstain, and such that only the result of the election is revealed, but the number of positives, negatives and abstains stays secret?
Are there some ways to do this without a thr... |
Let's define the following block cipher:
$C_n = M_n \oplus H(k + n)$ where $C_n$ is the nth block of ciphertext, $M_n$ is the nth block of plaintext, $H$ is a cryptographic hash function, and $k$ is the secret key.
Decryption can be performed trivially, by computing $M_n = C_n \oplus H(k + n)$.
Assuming a proper mode o... |
Can hash trees provide quantum resistant signatures to replace RSA for signing securely? What is the key size and how many times can we use same key?
|
As the title states, would the One Time Pad (OTP) be considered a cryptographic hash function?
|
When using Encrypt-then-MAC with AES and HMAC by password, and given 128 bits of payload with the ciphertext to store a random salt, which would be more secure:
Using PBKDF2 with then entire 128 bit random salt and generating 512 bits of derived data to split into a 256 bit AES Key and a 256 bit HMAC key.
or
Using P... |
I'm studying the Kryptos sculpture with its cryptographic puzzles K1 to K4.
I understand that the keyword "palimpsest" was reverse-engineered using the tableau (and brute-force computer processing), but Sanborn always said that all sections could be solved using pencil and paper.
There are theories about the Morse, bu... |
LastPass encrypts its data before sending it to their servers. The key for the data is generated using a combination of the master password and username.
How then can a one-time password be used to decrypt this data? The data on the server has been encrypted with the master password and username. Does this mean that La... |
The question of implementing peer to peer mental poker has already been asked on stackoverflow. And there appears to be an implementation called LibTMCG.
Also on this site a question was asked about problems such as clients disconnecting or refusing to act (show cards, bet/check/fold). LibTMCG seemed to not deal with s... |
In this table of the "Crypto++ 5.6.0 Benchmarks", for example, cryptographic algorithm performance is measured in cycles per byte for symmetric ciphers, and in cycles per operation for asymmetric ciphers.
What does "cycle" here mean, exactly? And does one AES or RSA decryption always need the same amount of cycles, or... |
I'm attempting to encrypt some information into our database to be later pulled back out and displayed to the user. Searching and reading up on different methods I found a post over at stack exchanged with example code for doing AES Encryption.
https://stackoverflow.com/questions/165808/simple-2-way-encryption-for-c-sh... |
The textbook proof for Elgamal encryption basically reduces to the Decisional Diffie-Hellman assumption (DDH).
Elgamal:
$Gen(.): x \xleftarrow{R} \mathbb{Z}_p$; $Enc(m,g^x): r \xleftarrow{R} \mathbb{Z}_p, U= m.(g^x)^r, V = g^r$; $Dec(U,V,x): m = U/V^x$.
Suppose I prove the secure of Elgamal (in the CPA security model... |
I want to generate a few random numbers using an LFSR. However, the LFSR output depends on the number of taps, so for a large period I use large (relative) number of bits. This causes the numbers to be as large as the period. For example, I would like to use a 16-bit LFSR to generate random 5-bit numbers. What is the p... |
In regards to NaCl, I asked DJB he had any intent to add a streaming API to an authenticated cipher. His response was obvious in retrospect, that one should never release a decrypted plaintext before verifying the authenticator.
However, this got me to thinking. Streaming is important — for instance, when working with ... |
I'm trying to implement an e-voting algorithm, which is described at the paper "Internet Voting Protocol Based on Improved Implicit Security" by Abhishek Parakh & Subhash Kak.
At the Example 1 described in the paper where we have m1=85, at the step 2 it says
"2. Choose randomly and uniformly a number r1 = 101
and compu... |
Can anyone shed some light onto the advantages/disadvantages of using Rijndael with 256-bit block size, as opposed to the 128-bit (AES) implementation? (please note: I'm not referring to key-size here).
These are standard implementations in Mcrypt. I'm vaguely aware that a larger block size can help to mitigate some... |
Can anybody help me to understand elgamal based decryption mixnet? Pure elgamal can be used in mixnet (re-encryption mixnet) and its very easy, and I have implemented decryption mixnet using RSA also.
See for example, http://courses.csail.mit.edu/6.897/spring04/L18.pdf
But I have failed to gather any idea on the implem... |
I've already sent my correct solution to a homework exercise from Dan Boneh's Introduction to Cryptography class on Coursera:
"Let us see what goes wrong when a stream cipher key is used more than once. Below are eleven hex-encoded ciphertexts that are the result of encrypting eleven plaintexts with a stream cipher, a... |
OK, I have a shadow file with a password that I know, it is 4 letters followed by two numbers. Using John The Ripper with OpenCL support, on a laptop with AMD Radeon Mobility graphics, how long would it take to brute-force it? What speed should I expect?
|
Suppose I devised the following challenge-response proof-of-work system:
A server generates a 2048-bit RSA modulus, and uses the "public" exponent (usually 65537) to sign a random nonce a fixed number of times, say, 256.
The server then sends the signed nonce to the client, along with the "private" exponent (which is m... |
I am trying to get my head around the circumstances under which a cipher is (or is not) semantically secure under a chosen-plaintext attack.
I can't seem to find a good reference explaining this.
I think I am missing a fundamental concept, so If I explain it as I see it perhaps someone can correct me.
Semantic security... |
What are the benefits and disadvantages of CBC vs. CTR mode? Which one is more secure?
|
Possible Duplicate:
Using CBC with fixed IV
I am using AES in CBC mode.
For some reasons I have some issues for transmiting the IV. So I am using a fixed IV.
If the first 128bits of the message, change on every message (like a timestamp).
Does that can moderate the issue of having a fixed IV ?
|
I'm trying to find a collision for the following (modified) Merkle–Damgård hash function.
Suppose we already have a hash function $h : \mathbb{Z}_2^{2·n} \to \mathbb{Z}_2^n$ for fixed length bit strings, with $h(0\ldots 0)= 0\ldots 0$.
The input $x$ (bit string, variable size) is divided into blocks $x_j$ of $n$ bit e... |
I could create a rainbow table for a particular salt value and still create a successful attack similar to one without salt value.
|
Suppose I have this cryptogram:
AEOLOMWSUOYCMKBSXNSKFSMDYBCSOBBKAEOLOMSXNSKCSOBBKVSWKCSOBBKHBKISXNSKZKZKAEOLOMWS
UOYCMKBSXNSKSXNSKQYVPVSWKCSOBBKHBKIOMRYBYWOYUSVYCSOBBKSXNSKQYVPVSWKCSOBBKHBKIOMR
YBYWOYUSVYCSOBBKSXNSKQYVPVSWKCSOBBKUSVYCSOBBKZKZKTEVSODZKZKWSUOAEOLOMOMRYSXNSKQY
VPVSWKCSOBBKJEVEWSUOQYVPHBKICSOBBKFSMDYBDKXQ... |
I'm doing modular arithmetic in a Java program, and I want to calculate the time complexity of the individual operations.
$$ c= a · b \bmod n $$
$$ m = a^{-1} · b \bmod n $$
How do I get an approximation of the time complexity here, for example for 256-bit numbers?
|
Quantum key distribution depends, if I don't err, on (irreversible) damages done by MITM's measurements on qbits. Now news.yale.edu/2013/01/11/new-qubit-control-bodes-well-future-quantum-computing says:
"The Yale physicists successfully devised a new, non-destructive measurement system for observing, tracking and docu... |
I heard encryption based purely on XOR and Rotation is inherently weak. The paper Rotational Cryptanalysis of ARX says:
It is also easy to prove that omitting addition or rotation is devastating, and such systems (XR and AX) can always be broken.
But I am not able to find any information on how to actually do it. Can... |
I want to compare two cryptographic algorithms. The first algorithm is RSA, and second algorithm is ElGamal elliptic curve cryptography. Now, I’m looking for a way to compare the speed of the two algorithms (time needed to complete calculations).
Someone told me about computing “time complexity”. Is that really an advi... |
I sometimes read in papers that a (sub-)group generator $g$ is taken from $\mathrm{QR}(n)$ instead of $\mathbb{Z}^*_n$, where $n = p \cdot q$ and $p$ and $q$ are prime. Is there a reason for this? What properties does $\mathrm{QR}(n)$ have? Is it an especially big subgroup?
|
I want to implement a point multiplication ($k \cdot P$) operation on FPGA. I have a BN curve $y^2=x^3+2$, and a scalar value $k$. The $x$ and $y$ coordinates of point $P$ are of 256 bits. In the double and add formulas, there are three main operations: addition, multiplication, and division. Each of these are mod oper... |
I'd like to use AES-GCM instead of HMAC for authentication and privacy in a token used in a web application, but I'm unsure how to securely tag each token with an IV. Is it safe for me to prepend the IV in front of the AES-GCM data, or do I need to protect it somehow?
|
Sophisticated and efficient steganographic schemes with images as cover are available. However, I wonder: are there any that use texts as cover instead?
If one could only transfer a few printable natural language texts due to constraints, using texts as the cover might be useful.
Does anyone know of such a scheme or ho... |
I have some code that takes a list of credit-card numbers, splits the number into two chunks, one chunk is 8 characters long, the other chunk is the remainder.
Each series of chunks is saved into individual files, for example my test data looks like (these are test CC numbers):
378282246310005
4111111111111111
42424242... |
The curve $E(\mathbb{F}_{47}):y^2=x^3+x+38$ has order $61$ and $61|47^3-1$ so the embedding degree of $E$ is $3$ and therefore the MOV attack, presumably using some sort of distortion map and a suitable pairing can be used to find discrete logarithms. Exactly how is this done in this case?
If a larger example would bet... |
Suppose that I have an AES key $K$, and I'm instructed to find a plaintext such that the first 32 bits of the plaintext are some string of bits $S_1$, and the last 32 bits of the ciphertext once the plaintext has been encrypted with $K$ are another string of bits $S_2$.
Is this difficult? Is there a known attack agains... |
I understand that for a stream cipher to be useful, there must be a way to verify that the message was not tampered with (bits were flipped by an attacker).
So, instead of using some cryptographic hash function, like SHA-2, with HMAC, what if I used a much simpler (and faster) hash function, like FNV hash algorithm, an... |
Assuming I'm using bcrypt to digest passwords, is any additional security gained by either encrypting or HMACing the resulting digests? By requiring a key to compare password hashes, I would expect that this would prevent any attempt at brute forcing sans the key.
The keys for this operation are actually stored somewhe... |
There are a few posts that I've come across that seem to imply that using regular encryption and a MAC might be better than using the newer AEAD (ie: AES/GCM) modes.
https://www.daemonology.net/blog/2009-06-24-encrypt-then-mac.html
https://blog.cryptographyengineering.com/2011/12/matt-green-smackdown-watch-are-aead.htm... |
I have a scheme that, long story short, uses AES in CBC mode to encrypt third-party credentials for user accounts with a password-derived key. It's been mentioned that the use of CBC mode is a vulnerability because it is susceptible to "padding oracle attacks"; the cipher, after being initialized by the legitimate user... |
My application requires an AES-256 key K for some secure operation. In order to avoid saving this key in application, I have implemented following scheme:
There are 5 individuals who enters their passwords in application. Lets call them PW1..PW5
Using these passwords, I have generated the key as:
K = KDF(PW1 || PW2 ||... |
I've been trying to reverse engineer Mega's (mega.co.nz) API calls. And stopped on the step where client needs to decrypt session id with provided RSA key. I can get key data, but I have no idea how to convert this data into actual key.
Here is my Base64 encoded private key:
BACLkf9qj1yTiX+Jrc7nlp8GMbTh9XnksdQgImr1kRaz... |
Or, is there a cryptosystem that is both order-perserving and additive homomorphic?
|
Let's assume that we have a secure PRNG. Is it "safe" to initialize it with password, or seed based on a password like SHA256(password)?
If yes, is it "safe" to generate an RSA or DSA key from it?
The idea behind this is to initialize a PRNG with a password, then use it to generate RSA or DSA keys. So, the scheme will... |
I was wondering if hashing a password with the password would be a good way of encrypting the password. So, the user must know his/her password to get the same result as the one in the database. Also, this would prevent decrypting of the password without the password... right?
I've read articles and other SO questions/... |
From Wikipedia:
For a 256-bit block, the first row is unchanged and the shifting for the second, third and fourth row is 1 byte, 3 bytes and 4 bytes respectively.
Why the change? Is there any difference than in using 0, 1, 2, 3 like the other keysizes?
|
Is there a length-preserving encryption scheme, that preserves the lengths of input sizes such that the length of the input plain text is same as length of the output cipher text ?
|
I have read about block ciphers, but I do not understand the topic completely.
Is a block cipher a way to send data or a way to encrypt data?
How is the data divided into multiply blocks before it is sent? Is the data partitioned before the encryption process or afterwards?
How long are the blocks? Can I choose any bl... |
I am wondering how can I secure communications between multiple peers over a public channel, like an IRC channel.
With two peers it is easy - they exchange their encryption keys and decrypt the secret messages using their private keys, but how would this work with multiple peers without creating excessive duplication o... |
Is there any cryptographic primitive bijective (one-to-one and onto) function for creating cryptographic tools like symmetric encryption/decryption, Hash code generator, MAC, HMAC and Random number generator?
|
I'm looking for a way for Alice to send a message or a file to Bob in the most paranoid way possible (over the internet).
It can be asymmetric or symmetric. But According to some articles, AES 128bit, RSA, ECC are all broken or will be soon (with the new NSA Utah center).
I found PHPECC library on GitHub: https://githu... |
What is the most secure way to let Alice "input" her private key, transfer it to the server and decrypt the message? (Then destroy the private key on the server)
Every connection is using SSL.
Exmeple:
Alice log on the website. She have a new "email" from Bob. (Everything is stored in a database, it's not an actual ema... |
Is this even possible? The RSA group is not cyclic, so usually you wouldn't find a generator for accessing all group elements.
What happens if you use the RSA group in a scenario where you want that the discrete log problem is difficult. If you cannot find a generator, you want at least find an element with a high orde... |
When constructing a PRF that has n bit input using the GGM PRG, why do we always have to recursively run the PRG using its previous output as a seed key n times. Instead, why don't we run the PRG n times, and use that as the output.
Any answers would be great. My assumptions is that it has something do with producing i... |
I am looking into the application of pairings in CPABE in particular. I've notice that the scheme uses a supersingular curve as the basis of the pairing. Looking through Ben Lynn's thesis for the Pairing Based Cryptography Library, there is only a single supersingular elliptic curve implemented, which is a Type A curve... |
Let $$(g,h=g^s,q)$$ be a tuple such that $g$ is a generator for a group $\mathbb{G}$ of ord $q$ and $s$ is uniformly random in $\mathbb{Z}_q$.
The knowledge of exponent (KEA1) assumption says that for any adversary $\mathcal{A}(g,h,q)$ that outputs a value $(C,Y)$ such that $C^s \equiv Y$ then there exists a extractor ... |
Given a database where we have usernames and passwords, we want to secure users' passwords by hashing them. We should not use only username and passwords in this hash, as someone having data from other sites that uses the same hashing function can come to the same results and thus know our passwords. If we try hashing ... |
AES comes with key sizes of 128, 192, and 256 bit.
But in Truecrypt or other crypto software we can use passwords of different length, even less than 128 bit or more than 256 bit.
How is this possible?
|
Anecdotally, most factoring algorithms have a corresponding variant algorithm that can be used to attack the discrete log problem using similar ideas.
Is there an analog of the elliptic curve (ECM) factoring algorithm, but for discrete logs? Something that uses similar ideas, but can be used to compute discrete logs m... |
Let's pretend that all digits of pi are known and arbitrarily long sequences of digits are trivial to get. Further, some mathematician proves that there are no patterns in pi. We could create a stream cipher by grabbing a piece of pi as long as our plaintext and combining the two with some function (such as XOR or modu... |
I understand that most stream ciphers, due to being applied with a simple XOR, are specially fragile against data tampering, and must be used with some MAC mechanism. So I am investigating the use of UMAC for this purpose.
I also understand that UMAC works by XORing an universal hash function based on a secret key with... |
Let me know a cryptographic symmetric stream cipher system with only two functions say S() and P() and it should satisfy the following conditions:
There will be two independent computers say M1 and M2 (no connection exists between them) and only one function should be stored in a machine.
For example: Function S() wi... |
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