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Lets say an application is using CBC mode without authentication. The application is generating cipher text. This cipher text can be manipulated by the attacker and then transmitted back to the application.
Without looking at the code, what is an easy method for the attacker to prove that a Padding Oracle or Decrypt... |
I have some questions from previous years exams, I hope you could help me with them. :)
Suppose that a protocol satisfies the properties of a $\Sigma$-protocol, except that it is only (plain) honest-verifier zero-knowledge. Show how to transform this protocol into a $\Sigma$-protocol for the same relation by assuming... |
So if I want to encrypt all the files in a folder with AES (same password) I take each file and generate the key schedule using PBKDF2. As the PBKDF2 algorithm takes in a salt then this salt should change (and thus the keyschedule) for each new file being encrypted. Now if I want to decrypt then I load the plaintext sa... |
I have some questions from previous years exams, I hope you could help me with them. :)
Let $g,h$ denote generators of a group $G$ of large prime order $n$ such that $\log_g h$ is unknown to anyone. Consider an instance of the 3SAT problem for Boolean variables $v_1, \ldots , v_l$, given by a Boolean formula $\Phi$ co... |
I am a novice programmer and am just finishing up an RSA encryption program that I am writing for practice. Currently I have the program generate a relatively small random value for the public key e. When adding the finishing touches, I realized that there was no point for e to be random. Is this thinking correct?
|
RSA-OAEP is IND-CCA2 secure (indistinguishable under an adaptive chosen ciphertext attack). Does it also have the INT-CTXT (integrity of ciphertext) and INT-PTXT (integrity of plaintext) properties?
I don't believe that IND-CCA2 implies these. Are they true for RSA-OAEP though?
|
Is there any asymmetric cryptography algorithm which will allow recursive encryption.
c1 = crypt(encryptionKey1, 'Hello world');
decrypt(decryptionKey1, c1) == 'Hello world'
c2 = crypt(encryptionKey2, c1);
decrypt(decryptionKey2, c2) == c1;
decrypt(decryptionKey3, c2) == 'Hello World'
Knowing first and second key p... |
Given an authenticated mode of encryption, when comparing a plaintext string against the contents of a ciphertext, which approach is typically considered safer?
Encrypt the plaintext and compare against the ciphertext, or
Decrypt the ciphertext and compare against the plaintext in $O(n)$
The former appears better to ... |
I'd like to understand a bit more about the AES key schedule if anyone would mind explaining that. For instance, why is the way the schedule generated (with recursive xors and occasional substitutions) more secure than say, using pbkdf2 on the key, then using it on the result, and on until there is enough data?
The rea... |
In a Non-Interactive $Zero-Knowledge-Proof$, the challenge is chosen
by the Prover.
I am trying to find a Non-Interactive Zero-Knowledge-Proof based on the following problem:
DISCRETE LOGARITHM
Input: Prime number $p$, generator $g$ of $Z^{*}_{p}$ , and $y\in Z^{∗}_{p}$ .
Question: find $x \in \lbrace1, . . . , p − 1\r... |
If I have an algorithm,RSA-Crack(), that, for a given RSA public key (n,e), is able to decrypt 1% of the messages encrypted with that key (without knowledge of the corresponding private key).Can there be an efficient algorithm that uses RSA-Crack() as a building block, and can decrypt any message - without knowing the ... |
I have some problems in understanding the "advantage" of AES-XTS compared to CBC with diffuser.
I read something about FileVault, in this paper they mention the two modes of operations XTS and CBC (with diffuser) and the advantages of XTS.
Both modes encrypt data units almost the same way. For CBC, the sector number is... |
Suppose there are three messages A, B and C of different length, that are 16 DWORDs in length when combined. I know the plaintext and length of A and C, and only length of B. Is it possible to take any advantage of this knowledge when trying to recover a preimage of MD5(A || B || C)? I'm targeting "raw" MD5 transform, ... |
Is there something special about the AES key expansion algorithm that makes it secure, or it is a compromise between security and speed? For example, say with a key I expand it by taking pbkdf2(key) or scrypt(key) as the next round, and scrypt(scrypt(key)) as the round after that, until I have all of my subkeys. Would ... |
I've been looking at the weakness with plain/textbook RSA, where the same message is encrypted and sent to multiple destinations. In this case, it is possible to recover the message.
Given that an attacker then knows the values of $m$, $c$, $e$ and $n$ in the following equation, is there any extensions which allows the... |
The usual implementation of AES first computes all the Round Keys sequentially starting from the key, and stores them in RAM for later uses. However, when enciphering a single block with a key that will be used for that purpose only, or when RAM is very sparse, or perhaps in hardware, it is advantageous to use the Roun... |
Is this true that whenever you design a protocol using a hash function, you must prove its security under the random oracle?
I mean, is it possible to devise a protocol $P$ using a function $H$, and then prove a theorem saying that $P$ is secure in a model $M$ given that $H$ is a collision-resistant function? What I m... |
In a situation where it is required to generate n number of keys deterministically from a single piece of seed information can we assume that b breached number of keys, no matter what the quantity would not help an attacker discover the previous nor next key in the set without the original seed data?
My initial thought... |
We can't trust RSA to encrypt our Emails so what is best post-quantum cryptography system as alternative for RSA which provide good security and don't be breakable? because McEliece cryptosystem looks break with 2^60.55 bit operations..
|
If Alice and Bob have a secure channel for key exchange and Mallory doesn't man-in-the-middle attack them, but in the future eavesdrops on their connection and sees the key exchange, can Mallory break it like RSA with a quantum computer?
|
I did a CRT challenge yesterday and there`s one problem I was unable to solve, probably due to my lack of understanding advanced crypto math.
It`s about RSA. There are ten given pairs of N and E (modulo and exponent). E is always the standard exponent 10001 (hex). N is a 2048 bit number.
The task: factorize all N.
Well... |
How can I benchmark RSA operations on my computer? I want to know about 4096-bit long keys on general computers. How many encryptions and decryptions are possible per second? All benchmarks I found only show 1024- and 2048-bit keys.
|
I understand the basics behind public key cryptography, in that each party has two keys - the public one encrypts, and the private one decrypts. What I cannot figure out is, How does the public key encrypt and not decrypt, but yet the private key can decrypt?I do understand the possibilities of this, but, does anyone k... |
Just for fun, I want to encrypt a message that will take about 10 or so years to decrypt. My idea is to encrypt a message with AES-512 with a password one million decimal digits long.
Knowing not much about cryptography, is this any more difficult to decrypt than a shorter password? (I'm trying to prevent brute-forcing... |
I saw some time ago a post discussing the issues surrounding encryption of speech/voice in VoIP and how it can leak information (can't find it now). Can someone provide an insight into some of the issues and how to mitigate them if one wants to use symmetric encryption to encrypt voice between two devices? Is asymmetri... |
Hi I have a problem with moving my blind signature implementation from educational (textbook RSA) to more practical (padded RSA) side.
David Chaums paper gives a following figure:
$r$ - blinding factor
$e$, $d$ - public & private exponent
$Blinded\ message = Message \cdot r^{e}$
$Signature\ of\ a\ Blinded\ message = Bl... |
I'm currently writing a paper about RSA (a self-chosen subject).
I'm writing about the key-generation in RSA, and I have problem finding the public exponent e.
I have chosen p = 61 and q = 53.
Then I determined my modulus n = p ⋅ q = 3233
and my phi(n) = (p-1)(q-1) = 3120.
What bothers me is that when I try to gener... |
So here's the concept. Rather than storing 2 keys and using a random IV, which presents its own problems (key rotation, ensuring no key is used in more than 2^32 cycles, sharing the keys, etc), is it OK to derive the cipher key, authentication key and IV from a master key? It wouldn't stop the need for key rotation pol... |
As I know, in Paillier cryptosystem, the encryption $c$ of a message $m$ is calculated as $c=g^m r^n \bmod n^2$.
Now, I am wondering if I can derive $g^m \bmod n^2$ given that I know $c$, $r$, and $n$?
It seems that the "$\bmod\ n^2$" operation does not constitute a finite field. Not every element has the correspondin... |
The OCB mode of authenticated encryption (used for example with AES) is the fastest way to provide authenticity and confidentiality without having to strive into questions like: Encrypt then MAC, MAC then encrypt, Encrypt and MAC.
So why it is not widely used and didn't become a standard?
|
I was reading some articles about attacks on RSA system and I wonder about some generalization of the following theorem.
Theorem (Coppersmith).
Let $N=pq$ be an $n$-bit RSA modulus, where
$p<q<2p$. Then given the $\frac{n}{4}$ least significant bits of $p$
(that is $\approx$ half of LSB of $p$) or the $\frac{n}{4}... |
A message may be accompanied with a digital signature, a MAC or a message hash, as a proof of some kind.
Which assurances does each primitive provide to the recipient?
What kind of keys are needed?
|
The difference between a digital signature and a MAC is non-repudiation. A message with a digital signature proves that only the sender could have signed the message, whereas a message with a MAC proves that either the sender or the recipient could have signed the message.
Can an OpenPGP implementation, such as GPG, be... |
Say I have
$k1 = "keyhere";
$k2 = "keyhere";
$rc4key = sha256($k1 . $seed);
$aeskey = sha256($k2 . $seed . $rc4key);
$input_data = "hello world";
$rc4 = new RC4 -> encrypt($input,$rc4key)
$aes = new AES -> encrpt ($rc4, $aeskey);
Meaning...
If I have two keys (1 rc4 and 1 aes), Is it more secure to en... |
I'm trying to calculate the size of an RSA public key in Ruby. I've retrieved the key in PEM format, and once I've decoded the base64 part from the PEM format, I get the size in bytes. What I find is that what I retrieve and the actual key size is off by 12 bytes, or 96 bits for that matter – for a 1024 bit key, I get ... |
In the Dolev Yao model for interactive protocols, the cryptographic primitive (encryption, for example) is considered as a blackbox.
Does blackbox here mean that the primitive is to be considered CPA secure, or does it even require CCA security?
My guess is that CPA is sufficient (and it is the minimum requirement), si... |
What is the need for two private/public keys in twin elgamal?
I'm relatively new and would need some help.
|
I am trying to find a protocol for this problem:
Three persons, $A$, $B$, and $C$, know secret numbers $s_{A}, s_{B}$, and $s_{C}$, respectively. They want to know whether their numbers are all different, but none of them wants to reveal his number to any of the others.
If there are equal numbers between the three, thi... |
On a practice question for my intro cryptography exam, it asks the following:
Assuming that keys are chosen with equal likelihood, the shift cipher provides:
A) computational security
B) perfect secrecy
C) semantic security
D) none of the above
I chose "none of the above", though I wasn't too sure. But I ... |
I'm currently carrying out a differential attack on the FEAL-4 algorithm, however I have hit a bit of a wall.
Basically I attacked the final round first ($K3$) using the differential characteristic of 0x80800000 which yields a differential of 0x02000000 with a probability of $1$.
I have found four possibilities for th... |
I read that we do not know if there exists an 8x8 sbox with differential uniformity = 2.
I suppose we cannot compute every possible sbox because there are $64!$ possible s-boxes. Am I right?
|
I've just started working with elliptic curves and ECSDA in particular, so my understanding of the underlying math isn't great. The thing I'm currently stuck on is trying to understand why replay attacks don't work on ECSDA.
For this scenario, the public key, $Q = x \centerdot G$, where $x$ is the private key and $G$ ... |
Previously we visited the benefits of elliptic curves for cryptography. Lattice based cryptography is starting to become quite popular in academia. The primary benefit of lattice based crypto is the resistance to quantum algorithms. Are there other benefits to lattice based crypto? For example, speed, ciphertext/key si... |
In public key crypto, the popular definitions of security (CPA, CCA1,2) depend on PPT adversaries. I'm trying to understand why adversaries should be PPT.
It's clear that adversaries should be at most probabilistic sub-exponential, because otherwise they could exhaust the message space. It's also clear that adversaries... |
Bob wants to send a message to Alice, such that Alice can be sure that the message came from Bob, but can't prove it to anyone else.
If I understand right, this means that the same message could have possibly also been constructed by Alice, but not by Eve (who can observe, change, remove and inject messages).
The usual... |
Do all $2^{\ell}$ (where $\ell$ is the bit length of the shift register) states always occur in a LFSR or can I choose my taps badly so some states are skipped and the period is shortened?
If so is there a way to prove the number of states that can occur in a LFSR?
|
Predicate encryption(PE) arrived as a descendant of attribute based encryption. Attribute based encryption allows the encryptor to embody a policy to the ciphertext (Ciphertext-Policy based encryption) and the receipent to receive a key from a central trusted authority according to his attributes. If the attributes do ... |
Suppose $g$ is a generator of an order $p$ cyclic group in which discrete logarithm is hard and $p$ is a prime (i.e., given $g^x$ for a random $x \in \{0,1,\ldots, p-1\}$, it is hard to recover $x$ except with $negl(\lambda)$, where $negl(\lambda)$ is a negligible function of the security parameter $\lambda$).
My quest... |
I have been wondering about the options available for managing passwords. However, they all seem to fail if the master password is compromised (which isn't a big surprise).
On one hand you have system's like LastPass which store all your passwords using a master password to encrypt them.
In other words, your computer ... |
I'm having difficulties understanding exactly what this protocol means:
$S \to D : \{N_S , S\}K_D$
$D \to S : \{N_S , N_D \}K_S$
$S \to D : \{N_D \}K_D$
"where $S$ represents the supervisor’s console and $D$ represents the door controller and the other symbols have their usual security protocol meanings."
I understand ... |
I'm trying to understand ECC from an IT layman's perspective and am trying to separate the theory from the standards, and understand why certain features are implemented or not implemented in the common ECC stacks.
Question
Namely, I'd like to know when should a non-standard ECC library (or related hardware) should be ... |
The NIST-Recommended Random Number Generator Based on ANSI X9.31 Appendix A.2.4
Using the 3-Key Triple DES and AES Algorithms has 3DES being used three times for each 64-bit block of random data desired, e.g.
$I = ede_K (DT)$, $R = ede_K(I \oplus V)$ and a new $V$ is generated by $V = ede_K(R \oplus I)$.
OpenSSL seems ... |
$N=p·q$ ($p$ and $q$ are prime numbers), $m_1, ..., m_x$ are the messages, $e$ and $d$ are RSA encryption and decryption exponents, respectively.
I am given $e, m_1, m_1^e, m_1^d, ..., m_x, m_x^e, m_x^d$.
Is it possible for me to factor $N$ or derive $d$ from the above knowledge?
My tentative answer is "no" because thi... |
Chapter II of Merkle's 1979 PhD thesis is titled "One Way Hash Functions." The chapter appears to be the first reference to cryptographic hashing. The chapter has no references. Is there an earlier reference that I am not aware of?
|
I just find this pencil and paper cipher 'Felix' and I want to know how secure it is?
EDIT
From http://web.archive.org/web/20110825142054/http://topcat.hypermart.net/papers/felix.txt
Felix a pencil-and-paper cipher
I. Synopsis
Felix is a `pencil-and-paper cipher' offering relatively good security for
causal use.... |
I'm trying to figure out the best way to generate a cryptographically secure random number between 0 and 200 (inclusive) from a cryptographically secure random string of bytes (ie. read from /dev/urandom or some such).
I could do random[0] % 201 but then numbers 0-54 would be more likely than 55-200 which would make th... |
For a project I am working on, I have access to a CSPRNG that outputs a random integer in the interval $[0, 2^n-1]$ for any integer $n$ greater than 0. I cannot use the zero values, so I have my RNG code in a while loop that runs until the random number is !==0. For small $n$ it is very likely that the while loop will ... |
Is there a big dataset containing RSA public $(n,e)$ and private keys $d$ and primes $p,q$ where $n = p.q$ ?
|
I was trying to understand RSA when I encountered the Euler Function. I do understand this: $\phi(P)$, where $P$ is a prime is $P-1$.
However it seems that for a number $N$ such at $N=P\cdot Q$ where $P$ and $Q$ are non-equal primes:
\begin{equation}
\phi(P\cdot Q) = (P-1)\cdot(Q-1)
\end{equation}
I'm having troubl... |
Here is the post that explains the failure for doing h(k||m) and I understand it.
But I don't understand how h(m||k) is subjected to collison attack, or birthday attack. Please explain?
|
I have been studying a Supreme Court case "IMS Health vs Sorrel".
In this case a Friend of Court brief filled by "Electronic Privacy Information Center" states that use of MD5 hash function to link multiple records together is suspect, since MD5 is broken.
I find this argument incorrect, the only use of MD5 (it is unkn... |
Suppose I have a random number (eg 625 467 921). I use it once to encrypt a message OTP style, and when I want to use them again, I reverse them (eg to 129 764 526) and use to encrypt the other message. What is the weakness of this scheme?
Again, suppose I have some random numbers (again, eg 625 467 921). When I want ... |
So I was just wondering in RSA, can the encryption exponent e be greater than ϕ(N)??
For an examples sake, lets just say N = 707, so p = 101 & q = 7. So, we have ϕ(707) = 600.
Can I have e = 707? because I can calculate d = 443 by de=1 mod 600.
I have seen it almost everywhere that 1 < e < ϕ(N). But my question is WHY?... |
This answer points out that certain key and block lengths were a requirement for the AES submissions:
The candidate algorithm shall be capable of supporting key-block combinations with sizes of 128-128, 192-128, and 256-128 bits.
My question is this; how can having a key length that is greater than the block size enh... |
This question relates to the underlying RSA assumption. Forgetting about the fact that Textbook RSA is deterministic, I am curious about the assumed strength of the RSA problem.
Does RSA hide all bits of the message, or are there some bits that can be easily revealed. Concretely,
$$m^e \space \bmod \space N$$
Can any... |
Lets say I have a seed named iv which has a decent amount of entropy.
Are there any glaring issues with the following?
First 64 bytes are generated by SHA512(iv)
Next 64 bytes are generated by HMAC_SHA512(iv, Previous64Bytes)
and so on...
Obviously if I needed "perfect" security I could use something like HMAC-DRBG (NI... |
Does FIPS 140-2 require specific key sizes, or does it have specific requirements for the data?
In other words, if I encrypt a file, how I can check whether it is FIPS-compliant or not? Does only the key need to be checked, or does the encrypted file have to be checked too? If yes, is it possible to elaborate on how to... |
In terms of security, would it be MORE or LESS secure to take, say, an RC4 output (or Serpent) or other, that is encrypted with one key, and to encrypt that output with AES (using a different key)?
> $Data -> Serpent -> key: $s_key = HASH_HMAC(sha256, "1st Key" .
> $salt1, "HMAC KEY1") = $S_Output
>
> $S_Output -> Ri... |
Lets say I want to tweak/alter the textbook RSA encryption function to create a pseudorandom function by pre-processing the input.
Suppose I do something simple like add 2 to the input before encrypting it:
$$c = (m+2)^e \bmod N$$
How do I know if this is not a secure pseudorandom function? Does this give any informati... |
I'm going to try and eventually factor RSA-100, but my current QS needs a lot of improvement, so I'm going to try and switch over to the MPQS.
I'm a bit confused as to how the MPQS works, which is correct:
1) Use the QS polynomial to generate X/Y pairs, then sieve with the "new" polynomial
2) Use the "new" polynomial t... |
Having some specific ECDSA curve and a private key, how does one calculate the public key? I am having a hard time finding the algorithm and equations for it.
|
We change the AES block cipher encryption:
we delete the key schedule algorithm
the user now provides a string of 1408 bits
we divide the string to 11 sub keys, and use them directly in the encryption part of AES as the round keys.
We call the resulting function $AES' : \mathbb Z_2^{1408} \times \mathbb Z_2^{128} \to... |
while working on tate pairing, i have to implement towering technique. like i have point p on F(q) and point Q(F(q^k)) (here embedding degree k=12 for BN curve).
instead of taking a point Q on F(q^12), i take this point on twisted curve E'(q^2).
finally i need to map this point to F(q^12),how can i use this towering te... |
I'm making a digital-asset manager written in ActionScript 3, it will be used to manage highly sensitive information. I'm using the AS3Crypto library (which has quite a good reputation) to implement AES encryption.
When I encrypt data using the AS3Crypto library, using AES-CBC, and a 256-bit key, I'm able to successfu... |
I understand that Blowfish is getting old, but is still a secure algorithm, and that AES is very popular, and is recommended by most people. My question is, how do the two compare when a 256-bit key is used for AES, and a 448-bit key (the maximum according to the standard) is used for Blowfish? Would Blowfish with a ... |
Imagine the following situation. There is an application for a microcontroller-driven system. The profits are made from manufacturing and selling the device itself. However, it is expected, that the users can later download software-updates from a public website, and install it (using a USB-connection, for example).
No... |
In Wikipedia, there is an article explaining Lenstra's factorization algorithm. As far as I got it, we choose some $e \in \mathbb{N}$ and a point $P$ on the curve and then calculate $eP$. While calculating, we must invert elements, and if that does not work, we are rewarded with a factorization.
So far, so good. Now, W... |
Historically hashes have been from a large set (say 256 characters) to a smaller set (256 bits).
Also, hash functions that are P-complete have no known parallel algorithm; they must be computed serially which ensures a certain amount of temporal cost in computing them.
Three questions:
What is the technical term for... |
Say I'm connecting to a web server secured with TLS but with a self-signed certificate. Accordingly, I call the owners of the server and ask them what SHA1 fingerprint they have.
They start reading out the hex digits to me and I follow along, but before reaching the end, I just say "That's fine thanks, no need to read ... |
I've been told that asymmetric cryptography requires that the message to be encrypted be smaller than its key length.
Why is this?
I know about hybrid encryption, which uses symmetric encryption to resolve this problem.
But I still want to know why public-key cryptography needs the data to be shorter than the key lengt... |
I am looking for an Authentication protocol for access control. Let's say both the client and server would share a symmetric secret (256 bit key) and the client wants to access the server. Access should only be granted to a registered client the server shares a key with and both parties should know whom they've talked ... |
Why is it important that $\phi(n)$ is kept a secret, in RSA?
|
When performed in binary Galois fields $GF_{2^n}$, Shamir's threshold secret sharing scheme produces shares that are each the same bit-size as the secret. Though the scheme is "perfectly secure" in that less than the requisite number of shares provide no information about the secret, in practice it does leak informatio... |
Assuming I already have a 256-key (32 char password) for AES encryption, comprised of random alpha-numeric characters and punctuation (95 possible ascii chars), generated by a decent PRNG, is there any reason to use a KDF to convert this into another key of the same length? Is a derivative hash in some way stronger?
O... |
Suppose that i share a common modulus $N$ with two users $u_1$ and $u_2$ with public, secret keys ($e_a,d_a$), ($e_b,d_b$).
Why then $gcd(V,e_b)=1$ where $V=d_a*e_a-1/$W and $W=gcd(e_b,d_a*e_a-1)$ and as a consequence with extended euclidena algorithm i compute $α,β$ such that $α*e_b+β*V=1$ and it comes that $α=d_b$... |
we don't want change standard just after every attack, now for AES 128bit blocks i think 16 round is secure, but what is best round amount ? we had attack for 7 round then 10 round and it going so on i think so is better we use a better standard. how many round you think we use is better for a long time ?
|
Suppose that $S=(E,D)$ is an additively homomorphic encryption scheme. Now I want to design a protocol $P$ such that given inputs $x_1,x_2,..,x_n$, the adversary $A$ (who can decrypt) can only learn $\sum x_i$ and nothing else. To do that, $P$ first generates random values $r_1, r_2,..,r_n$ such that $\sum r_i = 0$. Th... |
I was reading about the differences between the GCM and the CBC more here and I have a follow up doubt on the same.
In the CBC mode the person who performs the encryption is the one who provides the IV for the encryption -- and the IV is required to decrypt the ciphertext.
However, in GCM i read that the nonce value is... |
The functioning of the Internet as we know it nowadays depends very heavily on public-key cryptography, including several key root systems that depend on its asymmetric properties.
But what would it be like to not have that tool? Could a sufficiently advanced but less convenient private-key cryptography system still ma... |
assume we say 128bit keys are secure so a 16 character long password is safe, but if i even use lower case and upper case letters with numbers and special characters on my keyboard its about 80 different character i can choose, as we have 256 different byte in nature so it look like the 16 character random password i c... |
I am somewhat familiar with current research on fully homomorphic enryption schemes and their possible application to Cloud computing.
I've just noticed (somewhat late) that a marketing-savvy group of Physicists working on quantum information is approaching the same possible application: they call their approach blind ... |
Re-reading my copy of Cryptography Engineering for the holidays, I was struck by the following question about the Fortuna RNG:
Why require an entropy source specify which pool a random event should go in?
(For code, see the add_random_event method in this python implementation).
The book discusses why you wouldn't want... |
It seems to be believed that encrypting twice with a block cipher using an independent key each time is not as secure as you might expect because of the "meet in the middle" attack.
This is an attack with known plaintext. The theory is that the attacker encrypts the plaintext with every possible key, and decrypts the ... |
(The original question that was here was considered too confusing, unclear, and rambling. You can still view it in the edit history, but the content is no longer useful by itself, and cannot be reasonably reconstructed into a question suitable for this site. The question object is still here by decision of a moderator,... |
Ron Rivest posed a puzzle in 1999. MIT LCS35 Time Capsule Crypto-Puzzle.
The problem is to compute $2^{2^t} \pmod n$ for specified
values of $t$ and $n$. Here $n$ is the product of two large primes,
and $t$ is chosen to set the desired level of difficulty of the puzzle.
Note that the puzzle can be solved by perf... |
The mathematical definition of neglible and non-neglible functions is fairly clear-cut, but why they are important and how they are used in cryptography?
|
I am designing some cryptographic protocols and I am new to it.
Are there any well-known tools that can be used to model and design these protocols?
And also verify or analyze their validity?
If not a tool, is there any popular approach or formal method to design and analyze crypto protocols that are widely accepted?
... |
A Fully homomorphic encryption scheme needs to support an evaluate function that can do add and multiply operations on cipher text.
Can we do all kinds of complex operations on cipher text like search, sort etc using just add and multiply ?
|
I am working on a library (using standard primitives: AES256 CTR; HMAC with SHA256; PBKDF2 with SHA256, 128 bit salt, and 10000 rounds) to encrypt and decrypt data, given a password.
The encrypted data includes a header with version information and an HMAC (the header is included in the HMAC).
I am worried about exactl... |
(I am not a crypto expert, so I apologize if the terminology I use is incorrect.)
Suppose I have the following simple broadcast encryption scheme for securely sending content to $n$ authorized recipients using only symmetric-key algorithms:
each authorized recipient is given a recipient key (known only to the sender a... |
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