instruction stringlengths 32 27.2k |
|---|
After revoking a key and sending the revocation to MIT's keyserver, I noticed that the key is listed as such:
pub 2048R/XXXXXXXX 2011-01-01 *** KEY REVOKED *** [not verified]
Who is responsible for the 'verification of the revocation'? Does the owner of the key do this verification? If so, how is this accomplished? ... |
I'm reading the paper "Message Freedom in MD4 and MD5 Collisions: Application to APOP" about finding collisions for the MD5 hash algorithm involving the concept of tunnels as described in "Tunnels in Hash Functions: MD5 Collisions Within a Minute".
But I couldn't understand about the difference between point of verific... |
Suppose I choose $p=7$ and $q=11$.
This gives a public key of $p^2·q = 539$.
However, decryption occurs using a modulus of $p·q=77$.
If a person chooses to encrypt $500$ using my public key, how do I recover this value if the decryption modulus is so much smaller?
Is this a limitation of the Schmidt-Samoa scheme?
Is ... |
This comes following a discussion with a colleague.
My plaintext file plain consists of a about 100,000 lines of "all work and
no play...". It's size is: 2.2 MB.
Compressed it is: 5.4kB
I encrypt the original:
openssl aes-128-cbc -in plain -out plain.ENC
plain.ENC is marginally bigger than the original, which I would... |
Possible Duplicate:
How does one attack a two-time pad (i.e. one time pad with key reuse)?
I recently started to follow the cryptography class of Dan Boneh on coursera.org and the first part is talking about stream ciphers.
In general, we have an encryption which works as follows:
$$c = E(k,m) = m \oplus k$$
and $$D... |
I'm almost a newbie about RSA encryption, so my question could it be banal.
I'm beginning to create a licensing system for my software.
I need to distribute a crypted license file to many customers.
I was thinking to use RSA public key to encrypt license file (with OAEP padding or PKCS#1 v1.5).
The software that will b... |
I am going through the the Paper by Matsui on Linear Cryptanalysis of DES. In that, he says
$NS_{5}(16,15)=12$
And then in the next paragraph he says considering the expansion and permutation phases the following equation holds good:
$X(15)\bigoplus F(X,K)[7,18,24,29]=k[22]$
Can somebody help me understand this, becaus... |
I've read definitions of MAC and HMAC, but can't say I've completely grasped the differences.
What are principle differences?
When to use one and when the other?(Typical Use Cases)
|
When I was perhaps nine years, I borrowed a book from the library on various maths and CS topics. It outlined various simple ciphers, including one that I used a lot, just for fun. I can't remember the name of the book, or the name of the cipher, so I hope you can help me with the latter one.
It is a monoalphabetic sub... |
Im probably just not reading something again, but:
RFC 4880 says that a OpenPGP Public-Key Encrypted Session Key Packet (tag 1) is made up of
- A one-octet number giving the version number of the packet type.
The currently defined value for packet version is 3.
- An eight-octet number that gives the Key ID of the pub... |
I want to upgrade the security of some existing databases of users' authentication tokens strictly for the purpose of making sure that if the database is stolen, attackers will not be able to guess any but the weakest passwords in a reasonable period of time. I know there's not much I can do for people who choose "pas... |
I am trying to make a taxonomy of the different purposes of some cryptographic protocols. Generally speaking, the purpose of PIR, oblivious transfer and differential privacy--it sounds as if they were invented for the same purpose: "Give me the information I want without learning anything about this information".
Can ... |
Imagine that Bob sends a message to Alice for symmetric encryption to send to Charlie. (Only Alice and Charlie know the key.) Alice sends the encrypted message back to Bob to send to Charlie. Can Bob compare the plain text he sent to Alice with the encrypted version to guess, for example, what is Alice's AES key?
|
The Goldreich-Goldwasser-Micali construction allows to build a (cryptographically secure) pseudo-random function from of a (cryptographically secure) pseudo-random generator.
More formally, let $G: \{0, 1\}^s \rightarrow \{0, 1\}^{2s}$ be a length-doubling PRNG. Given a seed $s$, $G(s)$ returns a $2s$-bit string $G(s)... |
I'm studying Hash functions and Digital Signatures in sequence, and came up with some doubts about their usage.
First of all:
What is the difference between hashing a document and signing it?
And why aren't Standard Hash Functions considered fit for message authentication?
More specifically, considering Keyed Hash fu... |
Identity-based encryption schemes[*] seem to have great potential in high-latency, delay-tolerant and mobile, ad-hoc networks since they apparently seem to avoid the need for key negotiation and exchanges. Used solely for key exchange, they allow any pair of members in the same group (however you choose to define it) t... |
Suppose that you see all IP communication packets between two computers for a day, as they pass through a connecting router, and this amounts to 10MB. You additionally know that all data transmission follows the standard "RSA-1024 plus AES-128" protocol. To be even more specific, suppose you know only one computer is d... |
I've got a scenario where I need to encrypt many small (16-byte) plaintexts. I want to use AES-128 in ECB mode. Notably, each plaintext is guaranteed to be unique, though each may differ by only a few bits.
In this scenario, is ECB secure?
|
I am trying to get access to my eReader and I managed to get the passwd file.
root:$1$hdhxObPx$TYFuTKsB9GGIgo53rF4bi1:0:0:root:/:/bin/sh
bin:*:1:1:bin:/bin:
daemon:*:2:2:daemon:/sbin:
nobody:*:99:99:Nobody:/:
s3c2440x::507:507:root:/:/bin/sh
I expected to see a standard hash string there or just "x" but this reminds m... |
With Shamir's secret sharing is it possible to pre-define the points returned by the algorithm?
For simplicity if I have (k, n) where k=2, and n=4, and I have the points X,Y,Z, and Q. Can I create the coefficients so that X,Y,Z, and Q are the points returned from the algorithm.
If yes will it still be secure (or secure... |
I have an embedded system with AES-128 implemented in hardware. There is very little flash/RAM and the (8-bit) CPU runs relatively slowly. Public key crypto isn't a viable option. This system is connected to the Internet and can have one or more unique AES keys programmed at manufacture.
Are there any standard protocol... |
I cite from Fundamentals of Computer Security (Chapter 7 on Digital Signature, Paragraph 7.3 on RSA Signatures, page 289):
Multiple uses of the RSA Signature scheme tend to weaken it. The way out is to make subsequent signatures dependent on those previously generated.
Why is this?
Does it affect also the RSA Encryp... |
Let $h$ be a bitstring and let $P(h, n)$ be the n-bit prefix of $h$. A partial collision of length $n$, for a hash function $H$ is a pair $(x,y)$, such that $P(H(x),n)=P(H(y),n)$.
What is known about this type of collisions? I'm particularly interested in md5. Can rainbow tables be adapted to quickly look for these? Wh... |
As part of my cryptography course I came across an exercise that neither me or my friends could figure out.
The problem statement is as follows:
Let $p$ be a large prime of the form $p = 2q + 1$ with $q$ also prime. Let $g$ be a
generator of $\mathbb Z^∗_p$ and consider the discrete logarithm problem: given $h = g^... |
Many sources mention that IVs must not be reused with the same key in CTR mode, for encrypting 2 different pieces of data, because that totally destroys security - but I haven't found an explanation so far as to why this is the case.
The issue is obvious if the attacker can manage to obtain the plain text and its corre... |
Since MD5 is broken for purposes of security, what hash should I be using now for secure applications?
|
Can anyone explain me in details why does the following statement hold true in Chaum and van Antwerpen scheme for undeniable signature?
The probability that a dishonest signer is able to successfully
mislead the verifier in either verification or disavowal is 1/q where
q is the prime number in the signer's private... |
The well-known article about why we should use bcrypt for hashing passwords mentions the work factor - some parameter to the algorithm that determines how long one hashing should be in terms of number of computations. This as the article says allows for keeping up with Moore Law - when we have faster processors in the ... |
Wikipedia lists the following pseudocode for HMAC:
function hmac (key, message)
if (length(key) > blocksize) then
key = hash(key) // keys longer than blocksize are shortened
end if
if (length(key) < blocksize) then
// keys shorter than blocksize are zero-padded ('∥' is concatenation)
... |
Can you please explain me what is the reason of using nonces in the Needham-Schroeder and in the Kerberos protocols for Key Transport.
In particular :
Can you explain me the use of $N_A$?
And also, I suppose $N_B$ is used for the scope of letting $B$ know that $A$ shares the same key $K_{AB}$ and was able to decipher... |
Would it be difficult to find (cost, salt, input, password0, password1) such that
bcrypt(cost, salt, password0, input) = bcrypt(workfactor, salt, password1, input)
and
password0 != password1
where cost is not too small?
(If no, then the combination of bcrypt with PAKE described in this answer would be insecure.)
|
I've see many articles, most of them basically the same, praising Fujitsu for cracking what is referred to as a 923 bit pairing based encryption.
I understand that in comparing RSA to AES you've got something like a power of 10 for the key lengths to be equally strong. From what I read it seems that this pairing based ... |
I am using AES encryption (Rijindael) with Base-64 encoding in Obj-C and VB. I am currently using the following two projects to achieve this:
Obj-C: https://github.com/dev5tec/FBEncryptor/tree/3c739f18c94ea257aba5cb7b6a97f49af2589977
Visual Basic:
http://www.codeproject.com/Articles/15280/Cryptography-101-for-the-NET-F... |
I know that when you use a stream cipher you are just XOR'ing the plain text with the PRNG stream, such that you know if a specific byte is in position 3 of the plain text it will still be in position 3 of the cipher text. I know that this is not true for block ciphers in ECB/CBC/other modes except OFB. But why? W... |
I'm looking for a good place to start in cryptography and places to go to get free books etc on the topic.
I have been looking online but I always get stuck at some point or another. I need something that covers the basics better or a good explanation on how to understand the expressions/notation. It seems far from reg... |
For storing passwords, it seems that the use of intentionally slow hash functions (like PBKDF2 and bcrypt) is now recommended. This is because most hashes are designed to be fast, which also makes certain attacks on them parallelizable on GPUs.
Now I'm wondering if it would make sense to use slow hash functions for dig... |
Can Anybody tell me why the expectation value of the Index of Coincidence is the following?
For a cipher text string of length $L$, where $n$ is the number of
alphabet characters, $k_r = 1/n$, and $k_p = \sum_{i=1}^n p_i^2$
$$ E(IC) = \frac{1}{t}*\frac{L - t}{L - 1}*k_p + \frac{t - 1}{t}*\frac{L}{L - 1}*k_r$$
I forgo... |
It's been over 30 years since Rivest, Shamir and Adleman first publicly described their algorithm for public-key cryptography; and the intelligence community is thought to have known about it for around 40 years—possibly longer.
It's fair to assume that, during those 40 years, certain three-letter organisations have em... |
Are there any known collisions for the hash functions SHA-1, SHA-224, SHA-256, SHA-384, and SHA-512?
By that, I mean are there known values of $a$ and $b$ where $F(a) = F(b)$ and $a ≠ b$?
|
This is by no means a scientific observation, but it seems to me that stream ciphers receive a lot less attention than block ciphers. Is there any reason for this? (Is it because block ciphers are accepted as superior?)
Additionally, since there is no "AES" of stream ciphers, is there any reference of currently secure ... |
I am trying to get the idea of cyclic attacks againts assymetric RSA encryption.
Taken from Handbook of applied cryptography .
Let $k$ be a positive integer such that $$c^{(e^{k})} = c\mod n \tag{1}.$$
There for
$k-1$ it holds that $$c^{(e^{k-1})} = m \mod n \tag 2$$ where $m$ is the message for encryption $n$ is the... |
what is the capacity of AES in terms of File Encryption?
is it really good to encrypt a large files in AES? ex. I am encrypting a 8GB of File... is it still good to used AES?
is it still good to used AES-OFB in encryption of large files?
What also will be the issue if I used AES-ECB in file encryption? is the only iss... |
I'm not sure if what I'm asking is even a valid question but here goes.
Would it be possible to add a mechanism to an encryption algorithm that would mean it had to be a certain time of the day or a certain day of the year for the encryption to be able to be decrypted.
To Clarify, It should only be decryptable at a cer... |
When a hardware system is protected by a 4 digits password, what is the advantage of the attacker into breaking that system?
Isn't it $10*10*10*10=10^{4}$? If $\frac{1}{10^{4}}$ is the cost of such an attack then is this reasonable computation for the attacker? In my eyes this seems like a simple brute force attack for... |
I am developing a symmetric crypto library and have reached a roadblock. Looking at block ciphers, it is quite obvious that all block ciphers are trivially abstractable as a simple primitive consisting of:
a key schedule
a permutation function (which takes as an input a key, possibly a "tweak" and a data input)
This ... |
I have a cryptographic problem with the following characteristics:
I need to generate a set of relatively short messages; say 20 bytes in length
The contents of the messages themselves is not important to me as long as they are unique within a certain set.
These messages will be sent to a consumer.
The consumer must b... |
The Scenario
I have a client-side web application that bounces requests against a server-side API. For the sake of simplicity, every request must pass a username and password. This is similar to old school XML-RPC where the username and password are passed as parameters in every request.
However, as this is a REST se... |
I have finally managed to verify some simple PGP signed message blocks. However, I discovered that for some reason, my implementation limits me to verifying data that is 9-16 bytes long. no less. no more.
is there some instruction somewhere (RFC4880 or elsewhere) that specifies how to deal with plaintext data of any l... |
There is a profusion of articles proposing signature schemes without random oracles (see for yourself). What does that mean, and why does it matter?
|
How can I determine if I am generating a unique and strong Initialization Vector? If my mode is generating Keystream? Is there any scientific explanation in generating a unique and strong Initialization Vector?
|
Suppose Alice chooses a random Prime $p$ and a random private Key $a \in \mathbb{Z}^*_p$. By accident, she also chooses a random number $g \in \mathbb{Z}^*_p$, which is not a generator of $\mathbb{Z}^*_p$ and therefore
$$\langle g\rangle \subset \mathbb{Z}^*_p$$
as opposed to $\langle g\rangle = \mathbb{Z}^*_p$, which ... |
Are there any hashing functions that, if two are used in conjunction (with the same salts) will return the same response regardless of ordering?
I.e. are there hash-functions $H_1$, $H_2$ such that for all suitable salts $s_1$, $s_2$ and all passwords $x$ we have
$$ H_1(s_1, H_2(s_2, x)) = H_2(s_2, H_1(s_1, x)) $$
|
According to the US 2011 Wiretap Report, encryption — on the off chance that it is encountered — has been no hurdle to retrieving the content of a conversation.
Public Law 106-197 amended 18 U.S.C. § 2519(2)(b) in 2001 to require
that reporting should reflect the number of wiretap applications
granted in which enc... |
Background
One issue with modern security proofs is that they are usually asymptotic. In other words, such proofs are usually formulated as follows: For any polynomial-time adversary $\mathcal A$, we can select a large enough security parameter $n$, such that the probability that $\mathcal A$ breaks the system is a neg... |
I'm interested in a proof-of-work system that works well on standard computers without using the GPU.
Properties the system should have:
Seed based proof-of-work.
There is no distinguished challenger who can solve the problem efficiently. A typical seed is a 256 bit hash of a public key.
Minimize the advantage an atta... |
Assume there's an unencrypted message A, and an encrypted message B. You know that message B was encrypted using a simple XOR method of A with a private key K, resulting in message B. Thus,
B = A ⊕ K
Can I use Boolean algebra, i.e. truth tables, and sum of products to decode the key?
|
This RFC says the RSA Exponent should be 65537. Why is that number recommended and what are the theoretical and practical impacts & risks of making that number higher or lower?
What are the impacts of making that value a non-Fermat number, or simply non prime?
|
I'm creating an RSA key pair in Bouncy Castle and need to specify an int value for certainty. This Stack Overflow answer says it is a relative test for how prime the values are.
There is another answer that says this value should be adjusted relative to the key length.
Question
What are the correct values for certa... |
Suppose we have a RSA-type Modulus $n = pq$ with $p,q$ prime. We also pick a random public exponent $e$ with $\gcd(e,\varphi(n)) = 1$ and compute the private exponent $d$ with $de \equiv 1 \pmod{\varphi(n)}$. $(n,e)$ is the public key, $(n,d)$ is the private key. Just like RSA, so far.
Now we encrypt a message represen... |
How do replay attacks work in ECB mode?
I found this in Wikipedia:
"ECB mode can also make protocols without integrity protection even more susceptible to replay attacks, since each block gets decrypted in exactly the same way. For example, the Phantasy Star Online: Blue Burst online video game uses Blowfish in ECB m... |
Is there any probability/chances of repeated encrypted block in Output Feedback (OFB) mode?
Is there any existing documentation/studies about that? If it is existing, can you please provide me a link for that documentation, I want to analyze it carefully, I can't find some documentation about the probability of repeate... |
If a RSA certificate is created with a low degree of certainty, does the value of the exponent compensate for this?
I'm asking because certain implementations of key generation software hide the certainty value from the administrator, and I'd like to find reassurance in any other parameter.
If the exponent doesn't comp... |
I need to encrypt data that has a pre-defined header and footer structure, and furthermore the data follows pre-defined patterns. The header and footer structure follow a defined structure but cannot be left out because they are never truly equal. An example of this kind of data is an html file: it will in most cases s... |
Blum Blum Shub is a stream cipher that is provably reducible to the difficulty of factoring integers.
I'm wondering whether there is a similar construction for discrete logs?
For example, I could imagine having something like this being the update function for the internal state:
$x_{i+1} = g^{x_i} \mod p$
And then yo... |
While reading the Wiki page on RC4 I noticed that the key size must be in the range of 40–2,048 bits.
Why is that? Is there a reason it can't have a lower or higher length?
|
I need to send data between two applications. I've got requirement that says that data should be transmitted using secure protocol such as SSL/TLS. Data is sent using TCP sockets and I don't have built in SSL/TLS support. However, I'm able to encrypt content using AES and I'm also able to exchange small amount of data ... |
I'm very new to cryptography (and security in general, for that matter), but I had an idea that I'm sure is very flawed, but is worth asking. If a computer user, online account, etc, needs to verify a username and password, wouldn't this work well?
Upon signup, ask for username and password as usual
Hash username (cha... |
Is it a good idea to use a Blum Blum Shub Generator to create my initialization Vector (IV) in AES-OFB (Output Feedback Mode)?
|
Consider the following authenticate-and-encrypt scheme that uses AES-128 in CBC mode for encryption and AES-128 - based CMAC for authentication:
Two keys are derived from the master key k (16 byte): SHA256(k) = k1 || k2 (k1 and k2 are each 16 byte long)
The plaintext x is encrypted using AES-128 and key k1: E_k1(x) = ... |
Is there any 128-bit pseudorandom number generator available?
I tried the Blum Blum Shub Generator, but I can't produce a 128-bit pseudo-random number.
Maybe before I produce a 128-bit pseudorandom number, I need to input a 128-bit prime number which is hard to determine.
|
The Blum-Blum-Shub generator is a deterministic Pseudo-Random Bit Generator with security reducible to that of integer factorization.
Setup: Secretly chose random primes $P$, $Q$, with $P\equiv Q\equiv 3\pmod4$, and compute $N=P\cdot Q$. Secretly chose a random seed $x_0$ in $[1\dots n-1]$ with $\gcd(x_0,N)=1$.
Use: To... |
In terms of security strength, Is there any difference in using the SHA-256 algorithm vs using any random 256 bits of the output of the SHA-512 algorithm?
Similarly, what is the security difference between using SHA-224 and using any random 224 bits of the SHA-256 output?
|
I want to build a secure file storage web application. Users should be sure that server doesn't know how to decrypt files so encryption should take place at client side (i.e. in Javascript) and TLS will be used. Also public key cryptography is required as users should have possibility to send files to each other.
I pla... |
if i use the 2 of the same key with 2 of the same algoritm when encrypting in ECB like when i have 2 blocks of the same color and i encrypt the 2 blocks with the same color the cipher text should
not change
just like when i encrypt 2 blocks of the same information with the same key the cipher text would appear like i ... |
Diffie–Hellman offers secure key exchange only if sides are authenticated. For authentication, sides are using public/private key. So if side A knows the public key of the side B, then A can simply use that key to encrypt the message (or the new session key).
Why bother to use separate key exchange algorithm?
|
There has been some discussion about it being more practical to use SSL due to advances in hardware. From my understanding, stronger public-key encryption means that both encrypting/decrypting and breaking it (via brute-force or vulnerabilities) take longer.
Is the return (in security) for the performance loss of using... |
Given this description from RFC 4880 sec 5.1:
The value "m" in the above formulas is derived from the session key as
follows. First, the session key is prefixed with a one-octet algorithm
identifier that specifies the symmetric encryption algorithm used to
encrypt the following Symmetrically Encrypted Data Packet. The... |
I see there's a project to combine Quantum Key Distribution, Physical Unclonable Functions, and classical crypto, in order to secure a high speed (100Gb/s) optical link.
While there does not seem to be a direct combination of QKD and PUF in that particular project, I wonder if that combination could be used to solve on... |
I checked RSA's patent application, which was registered in 1983. As patents don't last more than 20 years, it seems to me it should be free. But my friend said to use RSA I have to buy a license from MIT. Is it true ?
|
we normally always encrypt by public key and decrypt with private key.
If i encrypt with private key, then its still secure as normal PKI ?
i mean known-plain-text will not take private key on the risk ? (for example when people know the plain text and signed message with private key, then private key is safe or will ... |
When we talk about a Number used ONCE (NONCE) in Initialization Vector (IV), is it required to use numbers only? Is is possible to use letters or special characters?
|
Consider that Alice wants to send a digitally signed message to Bob.
Mallory might be able to publish his public key under Alice's name and then impersonate Alice to send a message with an apparently valid signature.
But let's assume that Bob already has received Alice's correct public key.
Can Mallory still send a fak... |
I'm working on a background entropy collector for key generation that monitors hardware and produces an entropy pool.
Here's my list of sources:
Mouse position
Keyboard timings (i.e. time between keystrokes)
Network
Bytes sent
Bytes received
Datagrams sent
Datagrams received
Processor (per CPU)
Interrupts/sec
Que... |
I need to derive a key from a username and a password. These are the only two things I have access to. What I thought is using PBKDF2 with username as the salt and password as the master password.
Could someone help me evaluate / confirm this solution in terms of security?
Update: Since the salts are required to be uni... |
I am doing a research about secure communication protocols.
I would be interested to know whether a protocol exists such that it grants that the two end-points taking part to the communication cannot be traced (i.e. They can deny the communication ever took part).
Can anyone point out any relevant publication?
|
I understand that password hashes like bcrypt have the principal property of taking a long time to run, but I'm wondering what if anything about password hashes make them superior to merely running a fast cryptographic has a bunch of times.
In particular, why does bcrypt exist when I can just run SHA-256 100000 times? ... |
I am developing a symmetric en-/decryption routine written in c# for a database containing user-specific, sensitive information.
I have narrowed down the implementation to 3 different approaches, but simply cannot determine which is the "best". So, which of these is the most secure?
AES in GCM mode. Using either Bou... |
I am trying to build a public hash function (thus collision-resistant and preimage-resistant, and more generally behaving like a random oracle), with input a message $M$ of fixed size $|M|=m\cdot b$ bits, and output the hash $H(M)$ of fixed size $|H(M)|=h\cdot b$ bits, using as the single primitive a $b$-bit block ciph... |
In Advanced Encryption Standard, if I used "Counter Mode", how should I handle the nonce? Should I divide the nonce value into two? For example: I have 128-bit of nonce, should I divide it so I get two parts with 64-bit each?
The first 64-bit is my chosen nonce value (for example a0a1a2a3a4a5a6a7) and the second 64-bit... |
I was looking through block cipher padding methods, and found two good candidates:
ANSI X.923 - pad with zeros, then a final byte for the padding length, e.g. 00 00 00 04.
PKCS7 - pad with bytes that each show the number of padding bytes, e.g. 04 04 04 04.
Is there any benefit to using PKCS7 over ANSI X.923 padding, ... |
I was reading a question about combatting traffic analysis, and a thought occured. If I send random junk messages periodically, would that defeat traffic analysis?
The messages would contain some form of header to specify "this is junk", and would otherwise be comprised of random data of a random (plausible) length. In... |
for an embedded device I need to sign a 14-byte string and want to verify that string on the device.
Since there is already an AES-Library on the device, I thought about using the following scheme:
Use AES with a fixed IV and a fixed secret key to encrypt the following string:
"2byte Random Padding | 14byte data"
And... |
I am implementing an AES cipher in GCM mode in c# and have a few questions. My code is based on the code found [here] for reference. I'll copy in the relevant portions.
I am having difficulty understand the "additional authenticated data" (AAD) of the GCM implementation. (a) What does the AAD consist of? (b) where sho... |
I'm signing very small messages using RSA, and the signature and public key are added to every message, which requires a lot of space compared to the actual content.
I'm considering switching to ECDSA, would this require less space with the same level of encryption? And is the verification performance in the same range... |
I have noticed that different implementations of SHA1 give different results. As I'm currently programming my own SHA1 implementation (in MATLAB / GNU Octave), I wonder which one should I follow?
There are several implementations of SHA1 in Rosetta Code. Using the message Rosetta Code, most of them give SHA1 hash of 48... |
I have written some code to do AES in GCM. I currently manually append the tag property to the ciphertext, is this the proper way to communicate the authentication tag?
|
At university we were told that it is a bad idea to implement a MAC by simply concatenating a key with the data to sign and to run it through a hash function (e.g. $s = \mathrm{hash}(k||\mathrm{data})$ or $s = \mathrm{hash}(\mathrm{data}||k)$). The next ideas that were presented then were HMAC and CBC-MAC which are a l... |
i wrote this code:
// integer is a drop-in replacement of standard int
// http://calccrypto.wikidot.com/programming:integer
// it is an arbitrary precision intger
// integer::str(base, size) returns a string in that base, 'size' long padding the front with 0s
// base 256 means an ASCII string: 24930 (base 10) = "ab" (b... |
I'm studying the RC4 algorithm and I have the following questions:
On all questions assume that an expanded (2048-bit) key is used, and that the first 4096 bytes of the KeystreamIm are discarded.
After the above process, is the resulting S-box indistinguishable from a random permutation of the numbers 0 through 255?
As... |
What are the disadvantages of using random s-boxes?
In AES, the s-boxes had to obey certain mathematical rules, which? And why?
What security does using hidden s-boxes (GOST) or generating them from the key (Khufu) add?, and how do these secret and generated s-boxes defend against differential and linear cryptanalysis ... |
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