instruction stringlengths 32 27.2k |
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I use AES with AES/CBC/PKCS5Padding with the following encryption and decryption code sections in Java:
cipher.init(Cipher.ENCRYPT_MODE, keySpec, new IvParameterSpec(IV1));
cipher.init(Cipher.DECRYPT_MODE, keySpec, new IvParameterSpec(IV2));
where IV1 and IV2 are randomly generated 16-byte initialization vectors. As y... |
Assuming that $K_{n}$, $P_{n}$, and $C_{n}$ are individual bytes of the key, plaintext, and ciphertext respectively.
The first byte of ciphertext is computed like this:
$C_{1} = K_{1} \oplus P_{1}$
And the rest of the bytes are computed like this:
$C_{i} = K_{i} \oplus P_{i} \oplus P_{i-1}$
Is this a good way of encryp... |
Suppose Alice seeds a cryptographically strong Pseudo Random Number Generator with a truly random number, and keeps it secret. Alice then uses the output of the PRNG to generate several 256-bit numbers in sequence. Each of those 256-bit numbers is then used as an ECDSA private key, public keys are generated from them, ... |
I was looking at the algorithm for Twofish, and I noticed that in some places a XOR is used, but in others, they use "addition modulo-32." What makes modulo-32 special? Why not always use XOR? Why not always addition mod 32?
|
Below is the cipher text I am trying to break and as you can see its rather short which is why I am having so much trouble.
WOYFN ZCMSH VUVTG BFUTW ABTZP FHIMF TFOSU UXFQC HKVKG MPUUQ
MHRXI OVBRZ EPJYF KKVJW GEIOV HUKEB JUNSM THIMF TFKUB ULMMQX
What I know about this ciphertext:
Key is 6 characters long and repeats ... |
Is there a standard way to determine a complexity of the specified SAT problem? I'm researching algebraic cryptanalysis and came to solving multivariate quadratic equation systems using CryptoMiniSat. However it would be nice to evaluate a complexity of the full cipher equation system. Does it only depend on the number... |
Is it true that breaking a 1024-bit RSA key is as difficult as breaking a 128 bit symmetric key (e.g. AES)? I know that breaking a RSA key is equivalent to factoring the modulus $N$. To factor it, you have to see if any number between $2$ and $N/2$ divides $N$, right? But that would still be much greater than $2^{128}... |
Following @poncho's nice clarification of the RSA speedup here, let's see if I'm able to do the same in the case of the DGK cryptosystem:
We have pk = (n, g, h, u), sk = (p, q, $v_p$, $v_q$) which are generated as following:
we have 3 numbers, $k > t > l$
we pick u as the next prime greater than $2^{l+2}$ (having mo... |
I'm trying to implement NTRUEncrypt but encounter some problems. I've finished all the basic functions that are needed for the scheme base on this Document, but I can't find an algorithm to check the validity of the initial polynomial f.
If f is not qualified (inverse mod p or inverse mod q doesn't exist) then the func... |
For MD5 two different inputs are known that produce the same 128 bit hash value. However, these inputs are artificially created for this specific purpose.
For normal, real life inputs I believe no such collision is known?
When you only consider the first n bits of the hash however certainly such collisions are known fo... |
Bob and Alice each have a bit string they want to keep private. They each want to know what the bitwise AND of their two strings would be without telling the other or anyone else listening to their exchange their actual bit strings... how can they do this? Keep in mind that even once they both hold the AND of their tw... |
I am studying elliptic curves problems, which also includes study of related protocols such as ECIES. The problem is that I don't understand the notation $\|$. What does this operation mean?
Some stuff is mentioned on Wikipedia's Integration Encryption Scheme article, but this algorithm is better explained in the book... |
Lamport signature: Signing the message Note that now Alice's private key is used and should never be used again. The other 256 random numbers that she did not use for the signature she must never publish or use. Preferably she should delete them; otherwise, others gaining access to them would later be able to create f... |
SSL 3.0 and TLS 1.0 used an insecure scheme to generate implicit IVs when encrypting records in CBC mode: they used the last part of the previous record, a value that can be predicted by the attacker. This attack was demonstrated in the BEAST attack.
To avoid these issues, TLS 1.1 and later use explicit IVs, which are ... |
How to generate a session key between two nodes in two different subnets when the nodes don't know each other directly, using diffie hellman algorithm?
|
Let $p = kq + 1$ and $q$ be primes such that $log$ $q = n$, $log$ $k = n$ and such that the bit size of every prime factor of $k$ is bounded
by $log$ $n$. Let $g$ be a generator of the unique subgroup of $Z^*_p$
of order $q$.
$x \in$ $Z_q$ is picked randomly and you get $y = g^x$.
You may ask any number of questi... |
I have a HTML page(A Form) where user will enter his details. Details to enter are NameagesalarystateCity Now when user enters all details and click Button then I will create xml file containing the user details like
<root>
<name>abc</name>
<age>40</age>
<salary>20000</age>
<state>xyz</state>
<city>abc</city>
</root>
... |
The number of AES rounds increases with the key length. Why increase the number of rounds at all, and how were these round counts chosen?
|
I detailed here the DGK (Ivan Damgård, Martin Geisler and Mikkel Krøigaard) cryptosystem, and I managed to get it to work, most of the time...
The BIG problem that I am facing at the moment is that the key generation algorithm sometimes produces bad keys. The paper states that:
we generate $h$ of order $v_p v_q$ modul... |
Does the order of a block cipher cascade (e.g. in TrueCrypt) make a difference to the security provided, assuming independant keys?
For example:
Plaintext -> Rijndael -> Serpent -> 3DES -> Ciphertext
Plaintext -> 3DES -> Serpent -> Rijndael -> Ciphertext
The same ciphers, just ordered differently.
My intuition says no... |
What are the properties a generator $g$ should have to be secure for ElGamal signatures (original scheme)?
I am aware that it is poorly chosen and not secure when $g|p-1$ or $g^{-1}|p-1$, where $p$ is the large prime so that $g$ generates $Z_p^*$ and $g$ has maximum order (that is, $p-1$).
Are there other properties on... |
How can I know if I am generating a secure pseudorandom initialization vector?
Currently I am planning to generate a pseudo-random initialization Vector using current date and time - is this secure enough?
If the answer depends on the block cipher and mode of operation, I am using OFB mode with AES.
|
Suppose I'm developing an app to secure a lot of documents. These documents were encrypted (say, using AES) with a key X.
This key X is basically the password that the user enters before wanting to view any particular document, because that doc need to be decrypted using X.
If the user wishes to change the key X to som... |
I'm trying to figure out what the time complexity of RC4 encryption & decryption algorithms is, in big-O-notation.
|
I noticed recently that a couple of pieces of encryption software (TrueCrypt being one of them) don't directly use a hash of the password as the key for the block cipher. Instead, they generate a random key, use that to encrypt the data, then xor the key with the hash of the password and store the result within the enc... |
I need to store some sensitive data for a program. For each copy of the program, there will be a unique key for encrypting one (and only one) file using AES encryption (OFB). The key will not be changed (probably forever).
Is it secure if the hash value of the key is used as the IV?
Update:
The key is computer generate... |
Consider a common practically-collision-resistant hash function $\mathcal{H}$ (e.g. SHA-1, SHA-256, SHA-512, RIPEMD-160), perhaps based on the Merkle–Damgård construction as are the first three. We define a Message Authentication Code $\mathcal{C}$
$$(k,m) \mapsto \mathcal{C}(k,m)=\mathcal{H}(m\mathbin\|k)$$
where $\ma... |
Is every output of a hash function (e.g. SHA1, MD5, etc) guaranteed to be possible, or, conversely, are there any output values that cannot possibly be created from any input? In other words, are hash functions surjective?
If so, what guarantees this? If not, is it possible to discover such impossible outputs via an at... |
I noticed that PGP signatures have a "signed on" field. I was wondering if this is "trustworthy" information and if so how is it accomplished.
For example, I can't see how it could be trusted because someone could sign something a year ago and transmit it now or they could generate a fake date and I don't see how an o... |
i am creating some primitive demostration for ECDSA over small curve (p < 229). But my implementation have some weird issues. Verify process return false even if the signature is correct. Because I am testing it for some time, trying to find problem I discovered that verify work only if point order is prime.
So my que... |
If an encryption algorithm is meant to convert a string to another string which can then be decrypted back to the original, how could this process involve any randomness?
Surely it has to be deterministic, otherwise how could the decryption function know what factors were involved in creating the encrypted string?
|
Preface: This question was originally asked on Theoretical Computer Science and later on Computer Science. The kind people on cstheory.SE referred me to this web site. It is being repeated here in an attempt to find a satisfying answer.
Over the years, two novel encryption techniques have come to mind and been impleme... |
I'm playing around with work-factor hash functions, and I'm looking for a memory-hard operation to make it resistant to GPU / parallel hardware attacks. I considered a very large (i.e. 64K) s-box that gets shuffled based on the state per round, but I have a feeling that there are ways to optimise such an operation for ... |
I don't really understand Galois fields, but I've noticed they're used a lot in crypto. I tried to read into them, but quickly got lost in the mess of heiroglyphs and alien terms. I understand they're sets of the form $GF(p^n)$ for $n\geq1$ where $p$ is prime and $n$ is an integer. From what I can tell, they're defined... |
Linear feedback shift register tap charts are availale for registers of length 3 to 168. Does anyone have a chart for register lengths from 168 to 256 or beyond?
|
What's the standard way to express "$x$ knows about $y$", or "$x$ has no knowledge of $y$" in cryptographic notation?
Example (PRNG predictor):
$\exists f : P(f(G(k)|_{0..n}) = G(k)|_{n+1}) \geq 0.5 + \epsilon$, for non negligable $\epsilon$, where $f$ has no knowledge of $k$.
|
What is the harm if I publish an encrypted RSA private key publicly? Or in this case, what is the harm if I publish many thousands or millions of them?
Assuming that the private key is encrypted with a typical user password, the passphrase is some combination of password + user ID (which is not necessarily user-select... |
I found these images depicting the AES decryption process:
In the first image, the MixColumns step comes before the AddRoundKey step, while in the second image, the AddRoundKey will come before the MixColumns.
Which order is the correct one?
|
In the Add Round Key step in AES decryption, which part of the expanded key will I XOR first to the result of the SubBytes step?
Is it the 10th round key?
For example, is this the right order?
addRoundKey(subBytes,roundKey10);
addRoundKey(subBytes,roundKey09);
addRoundKey(subBytes,roundKey08);
addRoundKey(subBytes,roun... |
Do all the Cryptographic hashing algorithms operate only on integers (32 bit or 64 bit)? Is there any operation performed on Floating Point Numbers as well?
The reason I ask this is because I read here that there are no floating point calculations performed in hashing algorithms and hence FLOPS do not matter:
http://ww... |
i read this recently: http://www.newscientist.com/article/dn12786-quantum-cryptography-to-protect-swiss-election.html
and some parts of this: http://en.wikipedia.org/wiki/Quantum_key_distribution
they talk about direct fibre optic cable and evesdropping that seems passive.
i want to know whether quantum key distributio... |
I wrote my own cipher to encrypt messages. I would like to test a sample ciphered message to see how strong it is. Are there any tools for such task either in Windows or Linux ?
|
Say four people each have a public/private key pair that they can use to encrypt or sign messages. They have an anonymous way to post messages such that the others can see them. Malicious entities can post messages as well, but they can't forge the signatures these four can make.
I'm looking for an algorithm so that th... |
It is known that setting the secret key to a fixed, public value does not make MACs like CBC-MAC or GMAC into secure unkeyed cryptographic hash functions that could be used - for instance - for digital signatures.
In other words, the resulting hash function is not 1st pre-image, 2nd pre-image, and collision resistant.... |
Why is encoding using the private key used for signing? Wouldn't it make sense to keep the premise, that private is for decoding and public is for encoding? i.e. create a hash and threat it as a result of the crypting and decrypt it. The decrypted value being the "signature". Than when someone want to validate the sign... |
RFC 4880 describes the version 4 signature packet, tag 2, as
- One-octet signature type.
- One-octet public-key algorithm.
- One-octet hash algorithm.
- Two-octet scalar octet count for following hashed subpacket data.
Note that this is the length in octets of all of the hashed
subpackets; a pointer incremented by thi... |
Possible Duplicate:
Guarding against cryptanalytic breakthroughs: combining multiple hash functions
I'm a total newb to cryptography but after reading what I've read about it, I had a simple idea and I wonder if it has any merit. What if you encrypted using a selection of hash algorithms applied sequentially instead... |
The fact is I'm not quite sure if my question statement is true, however all the MAC constructions I know of (e.g. CBC-MAC, CMAC, HMAC) are deterministic, whereas many constructions for digital signature are randomized (e.g. DSA, ECDSA, RSASSA-PSS). I also know that RSASSA-PKCS1.5 is deterministic but still considered ... |
I am developing an application that sends messages which I want to encrypt and sign. The CryptoApi offers a function called CryptSignAndEncryptMessage.
The description says, what this function actually does:
The CryptSignAndEncryptMessage function creates a hash of the
specified content, signs the hash, encrypts the... |
I am trying to achieve the following:
Encrypted files are stored on users filesystem. The user uses my client to authenticate against a server. Once he is authenticated successfully he gets a token to decrypt the files.
Things I want to ensure: the user should not be able to cache the token for later use. like a one ti... |
A particular educational software program published by a U.S. government agency uses a variant of RC4 to obfuscate its data files (see Stack Overflow question). The variant of RC4 in question is identical to standard RC4 except at the beginning of the pseudo-random generation algorithm. The developer omitted the first ... |
Let's think of the following case:
A group of peers want to exchange messages with each other. They use public-key cryptography to sign and encrypt messages. Anyone with any name can join the network. There is no central trusted authority, such as a CA that could issue certificates. When a peer joins, he publishes ei... |
In the SHA hash algorithm the message is always padded, even if initially the correct length without padding; the padding is of the form "1" followed by the necessary number of 0s.
Why is it necessary that the message always be padded?
|
I'm currently working on an application that requires me to add two ECDSA private keys in order to make a new private key. The result has to have the property, that its corresponding public key is the same as one would sum the public keys corresponding to the first private keys.
I managed to get most of that going, but... |
I was given a ciphertext and now I am trying to break it via looking for the keyword.
This is a keyword cipher. So:
PlainEnglish: ABCDEFGHIJKLMNOPQRSTUVWXYZ
If keyword is HELLO,
CipherLetters: HELOABCDFGIJKMNPQRSTUVWXYZ
So, I had done a little frequency analysis where I've managed to get the percentage of most frequent... |
In normal LFSR, the state is a function of the initial seed, taps positions and time, nothing else. I've seen a modification of LFSR that works like this:
TAPS = const
MASK = (1<<L)-1 #L=bitlength of state
def parity(x):
return (number of ones in x)&1
def tick(state):
b = parity(state & TAPS)
return (... |
Say I have a request-response protocol and the task to make it immune to replay attacks. The requirements are as follows:
The defense mechanism cannot rely on the clocks of the parties.
The defense mechanism should work even when requests are not sequential.
No party can store more than 1KB of data at any given time f... |
For this question, the following caveats and assumptions hold:
There exists a 2048-bit RSA key pair used exclusively for signing/verification
The private key is kept completely private
There exists a group of users who have the public key
There is a group shared password
I (mostly) understand the functional difference... |
I want to combine encryption and MAC.
For encryption I use AES-256 with CBC and PKCS5Padding.
For MAC I use HmacSHA512.
I use the Encrypt-then-Mac approach (calculate MAC over the ciphertext and deliver it with the ciphertext)
The algorithm should be able to process streamed data, and if I calculate the MAC once over t... |
Is the uncompressibility of encrypted data a necessary property for a good cryptographic algorithm?
To make a crude experiment, I encrypted an 8K file with all 'A' and then compressed both the encrypted and the unencrypted file.
The compressed unencrypted file went down to less than 200 bytes while the conpressed encry... |
Being very new to C++ and cryptography, I finally managed to implement a version of the Vinegere algorithm. I would like to try something a bit more complicated. I have looked at AES and DES and others like them, but I was wondering if there is something simpler. Something that might use some of the same basic ideas as... |
A friend just showed me how to combine padlocks to achieve a lock that opens when k out of n people turn their keys.
I was wondering if there was something similar for encryption; using n or fewer public keys encrypt a piece of data so it can only be unlocked if at least k out of n specific private keys are applied.
I'... |
Let's say I would like to communicate with my friend using asymmetric/public-key encryption, e.g. RSA.
(Note: I do realize that in practice this is done through an intermediate symmetric key, but this question assumes we only use asymmetric encryption.)
Say I try to do this: I slice up my data into 2n-byte blocks (padd... |
Can I protect against the failure of a block or symmetric cipher by chaining different techniques together? If so what implementation details should I be aware of?
Are some combination of ciphers better or worse than others?
In my case I'm not concerned about the CPU expense, but am more concerned about defending ag... |
I need a problem that has one and only one solution, such that the solution is hard to find but easy to verify. I need to be able to generate the problem deterministically from a random seed.
So essentially, I want to be able to do this:
A random value is produced.
One can then search for the "correct answer" to the r... |
Alice securely gives Bob a secret key so they can exchange 10 different messages encrypted with RC4. (Messages will include a counter for uniqueness and a MAC for authentication.) For each message exchange, Alice and Bob both start by permuting the standard byte array using the secret key (ie, the "KSA" key-schedulin... |
How to remove padded value in Decrypted Message?
I am using AES Algorithm.
Let's take this as the decrypted message:
"abcdefghijklmn "
There is a 2 space in that decrypted message which is equivalent to 0x00.
how can I removed that value? during decryption to show the exact message before it was encrypted.
I am using... |
I have been reading about the 3DES algorithm and I cannot understand one part. In 3DES we do following operation: $$C=E[K_3,D[K_2,E[K_1,P]]].$$
Where $C$ is ciphertext, $P$ is plaintext, $E$ is DES encryption and $D$ is DES decryption.
In the second part we have the decryption with $K_2$. How can we decrypt a cipher wi... |
Possible Duplicate:
Is SHA-512 bijective when hashing a single 512-bit block?
Is there any guarantee that there are no collisions for all 512-bit input values for SHA-512 (every 512-bit input has a unique output), or just that they are highly improbable and can't be algorithmically deduced?
|
Possible Duplicate:
Removing Padded Value in Decrypted Message
I tried to encrypt and decrypt a file in ECB mode using AES Algorithm but I encountered one problem during decryption, I don't know how to remove the padded value.. because every byte in a file is unpredicted.. I am only using 0x00 in padding.
how to re... |
DJB's nistp224 program purports to be an implementation of elliptic curve Diffie-Hellman relative to the standard NIST P-224 elliptic curve.
To the best of my understanding, ECDH relative to this curve should produce 225-bit public messages (compressed points consisting of a 224-bit x-coordinate and a 1-bit y-coordinat... |
My assumption is that S/MIME almost always utilizes certificates as follows:
My certificate can be used to allow people to encrypt messages and send them to me.
My certificate (the same certificate) is used by me to sign messages and send them.
Is there an RFC reference that specifies this is a requirement for S/MI... |
I'm writing a one-time pad encryption program because I got really interested in the idea of "encryption which has been proven to be impossible to crack if used correctly".
I'm writing the program just for fun, as programming and cryptography are my hobbies. Therefore, I don't expect the program to be used for highly ... |
I have a question about attacks on the
implementation of cryptographic code that are enabled by compilation and compiler-optimisations. I am aware of this. Would
anyone be able to point me to other examples? In particular, are there examples of timing attacks that are enabled by compilation (in particular by compiler o... |
Why is there a requirement of "Non-Linear functions" as a component of many popular block ciphers (e.g. the S-box in DES or 3DES)?
How does it make the cipher more secure?
The only intuition I have is a non linear function can have many roots (solutions). E.g. for a non linear $y = F(x)$, if attacker knows $y$ to find ... |
(Hand moved from stackoverflow.com,due to suggestion)
Since breaking password hashes has become a new passtime for scriptkiddies, I thought of the problem and came up with a novel(?) idea.
store the pass as offset+number instead of hash
the number is a product of two large primes
the password is converted into a numb... |
I want to learn whether or no there is a cryptographic primitive,scheme assumption that is based on the following hard problem if it is hard . By hard we mean that we have a polynomial adversary: The attacker obtains a number $\sigma$ . In order to reverse engineer that or to go one step further for the cryptanalysis ... |
One of the typical approaches to computing a salted hash is this:
hash(salt+hash(secret))
where hash is something like SHA-256 hash function - taking any size input and returning fixed size output. What's the need for the hash(secret)?
Why can't I just do this:
hash(salt + secret)
where + is simply concatenating two by... |
I have two pseudorandom generators:
$f_1$ takes a random seed $l_0||r_0$ $\in \{0,1\}^{160}$ as input and outputs $r_1||r_2|| \dots ||r_k$, where $l_i||r_i = \operatorname{SHA-1}(l_{i-1}||r_{i-1})$ and $l_i, r_i \in \{0,1\}^{80}$
$f_2$ takes a random seed $s \in \{0,1\}^{160}$ as input and outputs $t_1||t_2|| \dots ||... |
Having finally figured out how to implement the Tiny Encryption Algorithm in C++, I wonder what to do about padding the key and the plaintext.
I know that there are various ways of doing this, but is there a "default" way to do this or does one make a choice?
|
First, just to make sure I understand "salting" correctly:
You randomly generate a string to append to the password before hashing it, so as to increase its length and make precomputed tables much less useful in cracking them.
Assuming my understanding is correct, then I'm having trouble how LinkedIn salted their passw... |
I am planning on encrypting a message then signing the message so the recipient can authenticate the source. Reading this article has me concerned that I'm doing something wrong.
My current plan is to use OpenSSL to do the following:
Create a random key
Use key to encrypt message with a block cypher
Encrypt key with r... |
I'm trying to implement this protocol:
Alice has her permanent key $K_1$. She computes $E(K_1, P)$.
She wants to share $P$ with Bob, Carol and Dave. For each of them she:
2.1. Generates $K_2$.
2.2. Computes $E_k(K_2, K_1)$ as $C_k$ and sends it via a secure channel.
2.3. Computes $E(K_2, E(K_1, P))$ as $C$ and sends i... |
I am very confused between the concept of known-plaintext attack and chosen-plaintext attack. It seems to me that these two are the same thing, but it definitely is not.
Can anyone explain to me how these two differ?
|
From this excellent answer I learned (correct me if I am wrong) that when writing a block cipher with say key size 128 bit, one has to pad the password given (variable size) so that it becomes exactly the 128 bit that is needed. I had thought that one would just add zeros or repeat the password until the length becomes... |
Does the same encryption algorithm given the same plaintext always produces the same ciphertext?
Does this cause any security flaws?
|
In MD5, there are four rounds. After every round, why do we need to add the computed $Q$ values to the initial values and then take this value as input to the next round. For example after the first round, we compute
$$Q^{\text{new}}_1=Q_{60}+Q_{-4}, \ Q^{\text{new}}_2=Q_{61}+Q_{-3}, \ Q^{\text{new}}_3=Q_{62}+Q_{-2},... |
Sha256Crypt / Sha512Crypt are designed based on ideas of BCrypt but use SHA instead of Blowfish because of political requirements.
The Sha*Crypt algorithms have the advantage that they are used in /etc/shadow on all common Linux distribution.
Do the Sha*Crypt algorithms have the same properties concerning memory use wh... |
I have to encrypt some very short messages (approx. 5 characters) and I would like the ciphertext to be as short as possible. I am currently using AES but the initialization vector (IV) is making my minimum cipher text be 32 bytes, even for plaintext of 1 byte.
Can I do better than 32 bytes?
|
While developing some code that uses the .NET AesManaged algorithm, I made some mistakes but was surprised at the results.
My encryption was correct. I was generating a random IV block and writing it to the file (without encrypting the IV). Then I was encrypting the plaintext and writing it.
The decryption was wrong ... |
I'm calculating a SHA2 hash of a certain sensitive key value. I need to store files on disk using this hash a directory path prefix. So lets say I hash the key value 150023, I get a 32-byte value which in hex is 64-characters long - quite a long filename.
What's the shortest string I can get of this 32-byte hash, that ... |
What is the difference in the purpose of DH and RSA? Aren't they both public-key encryption?
|
I'm new to Cryptography so please free to edit my question for clarity and add the appropriate tag.
I'm trying to research if the following is possible. Suppose
John has a message that he encrypts to share with more than one
recipients.
The message is different, i.e. it's unique to the recipients
(though the recipie... |
Which ciphers $c_k$ enable one to define a joining function $f_{c,k}$ such that:
$$
f_{c,k}(c_k(p_1), p_2) = c_k(p_1 + p_2)
$$
That is, the result of joining some known ciphertext $c_k(p_1)$ with a plaintext $p_2$ produces the same ciphertext as the concatenation of the respective plaintexts? Whilst there is some flex... |
Why does the TLS protocol use different symmetric keys for receiving and sending data?
Isn't it enough to have a single key used for both reading and writing?
|
In cryptography, an elliptic curve is a group based on a finite field $GF(p^k)$; this group has $n$ elements on it, and we work on a prime-sized subgroup of size $q$. We denote the value $h = n/q$ as the cofactor of the curve.
My question is: why would we ever want to consider using a curve which has a cofactor $h>1$?... |
Can anyone provide an extended (and well explained) proof of correctness of the RSA Algorithm?
And why is it needed?
I can't say that this or this helped me much, I'd like a more detailed and newbie like explanation, if you don't mind too much... ;)
|
What is the difference between encrypting something and hashing something? in what situations would I want one or the other?
|
Is there any publicly known software for differential cryptanalysis over some cryptographic building blocks as blocks ciphers or cryptographic hash functions
|
Digital certificates are used quite commonly these days, for signing files. They are used by various operating systems to ensure reliability and security. For example, Android requires that each of the apps submitted on the Android Market is signed with a certificate, and any updates are signed with the same certificat... |
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