-1
votes
2answers
52 views

Output of a Feistel network with all “0” round function

What is the output of an r-round Feistel network when the input is $(L_0, R_0)$ and each round function outputs all 0s, regardless of the input?
1
vote
0answers
28 views

How to encrypt letters less than block n using Hill Cipher

I am learning about Hill Cipher and know that it is a block cipher where each block of n letters (considered as an n-component vector) is multiplied by an invertible n × n matrix, again modulus 26. ...
0
votes
0answers
41 views

Need help solving a shift cipher problem?

A three letter alphabet {a, b, c} has probabilities p(a) = .5 and p(b) = p(c) = .25. A shift cipher is applied to pairs of letters. More precisely: plaintexts consist of two-letter sequences of ...
1
vote
0answers
58 views

Is it safe to derive a password from a signature provided by ssh-agent?

I'd like to use a password-based system on a remote host (accessed via SSH) without having to copy-and-paste the password and without storing it on disk. Using the system with some other form of ...
-1
votes
0answers
45 views

Create collision examples with MD5 hash with salt

I'm using the following lines to create a hashed string String source = String.format(%s %s %s", salt, firstPart, secondPart); byte[] bytes = md5(source); ...
0
votes
1answer
48 views

Key management protocol for end-to-end security on Advanced Metering Infrastructure

I am currently working on a research on end-to-end security implementation for Advanced Metering Infrastructure (AMI). Pardon me if I a bit off topic or not asking the right question as I am ...
1
vote
1answer
56 views

Can Diffie-Hellman be scaled up or force-multiplied?

I'm not too familiar with the math involved with the exchange of keys, I've read it over several times, but math isn't my strong point. My understanding is that smart people are hard at work to ...
2
votes
0answers
54 views

Generic group model: use of polynomials in the proof of the master theorem

I've been looking at the paper of Boneh, Boyen, Goh Hierarchical Identity Based Encryption with Constant Size Ciphertext which contains a general theorem (Theorem A.2) about the advantage of an ...
0
votes
1answer
43 views

How to calculate the entropy of passwords? [duplicate]

Here is a cartoon about password entropy. http://xkcd.com/936/ I dont quite understand how the entropy is calculated in the cartoon assuming they are calculate correctly. But in general, I dont have ...
1
vote
0answers
40 views

Does NSS fully implement PKCS 11?

I am looking towards using NSS in a Linux application that makes use of a TPM (HSM). So, I am checking the support of PKCS 11 in NSS, at least for the management of Elliptic Curve keys, signature with ...
-1
votes
0answers
45 views

ECC encryption with Miracle Library in C [closed]

I want to use miracle library in C for simulate some Algorithm. these algorithms are ECC encryption in different coordinate. I have two algorithms that should give me the same output . But I don't ...
6
votes
4answers
2k views

What is the recommended replacement for MD5?

Since MD5 is broken for purposes of security, what hash should I be using now for secure applications?
1
vote
2answers
65 views

RSA-KEM construction

"Create a random key for CCPA2 scheme, encrypt m, send it along with a PK encryption of the symmetric key. " Say in the process, the KDF is HMAC, then: get a random key (128-bit) C1 = encrypt ...
-1
votes
1answer
44 views

How to use the key from a Diffie Hellman exchange? [on hold]

I watched a YouTube video about Diffie-Hellman called "Diffie-Hellman Key Exchange", and it said after doing some modulo operations with the public modulus and generator and the random private ...
-1
votes
0answers
50 views

Bouncy Castle and Salsa 20

I want to use Salsa 20 in Java, so I downloaded Bouncy Castle, and... it makes no sense to me. I've got it working, but most of my choices were essentially random. But I can't see there anything ...
1
vote
1answer
60 views

Is it possible to 'fake' time for TOTP? (Time-based One-time Password)

TOTP (Time-based One-Time Password) Algorithm is used in Two factor authentication. I understand the algorithm and that current time is used as a variable to generate a token. Wiki page for reference: ...
2
votes
0answers
39 views

online Vickrey auction using remote coin flip

Is there any published work on implementing a online auction, which uses "remote coin flip" to prevent auctioneer cheating when choosing winner and bid value? Is there any possible way to use remote ...
0
votes
0answers
41 views

Forward Secrecy with pseudorandom functions

Let $H_1$, $H_2$ be keyed hash functions (e.g. $H_i(x) = SHA_{256}(s_i||x)$ for pseudorandom $s_1$, $s_2$). Let $s_n = H_1^k(s_0)$, $k_n = H_2(s_n)$, where $s_0$ is a secret (pseudorandomly chosen ...
1
vote
1answer
44 views

SpongeWrap without padding and frame bit

Assuming all inputs are same length as rate except last can be shorter. Is it necessary to pad every input (not just last) to sponge for authenticated encryption to be secure? Is this just, because ...
1
vote
2answers
70 views

How do RSA and ElGamal key sizes compare?

I have a rather silly question regarding the comparison of RSA with ElGamal over integers. If you want to compare their performance in the same level of security, does the modulus of both of them need ...
8
votes
2answers
2k views

How does order-preserving encryption work?

Order-preserving encryption (OPE) is, apparently, a method of encrypting data so that it's possible to make efficient inequality comparisons on the encrypted items without decrypting them. I've been ...
3
votes
1answer
264 views

Non-linearity of a boolean function

What's the definition of non-linearity of a boolean function? Roughly saying it is minimum number of times it equals any affine function. But I don't get it mathematically. For example, if $f = ...
1
vote
1answer
210 views

How costly is to find millions of large prime numbers for RSA?

Consider I need to assign a large distinct prime number to each element in a large set. This must be deterministic so the function always gives me the same prime to the same value. What is the most ...
2
votes
0answers
43 views

How to compute the decompositions used in fast FHE bootstrapping?

Leo Ducas and Daniele Micciancio's recent paper "FHE Bootstrapping in less than a second" gave an exciting result that one can compute the `atom operation' of Fully Homomorphic Encryption (i.e. ...
4
votes
1answer
253 views

How secure is this use of Ziv-Lempel encoding?

I'm reading patent application US 20120278897 A1 — “System and method of sort-order preserving tokenization”. Near the bottom they describe their token generation algorithm, which basically involves ...
-2
votes
0answers
40 views

Encryption function that returns a unique number based on 3 ints [closed]

I'm looking to write down a function that takes 3 integers as input: X, Y, and Z, and returns a unique integer based on those 3 integers. Note that X, Y, and Z are not interchangeable. Any ideas ?
0
votes
0answers
15 views

Isn't 'exponent' only present in MSME equations in Groth-Sahai framework?

Below are different types of equations in Groth-Sahai framework. All three instantiations, viz. Subgroup Decision, SXDH and DLIN allow to commit to exponent. But, isn't the concept of exponent only ...
1
vote
1answer
47 views

how can convert Affine to Jacobian coordinates?

Sorry . I know my question is very elementary but please explain for me :( I have a point in affine coordinates . (x,y) what should I do when I want to show it as (X,Y,Z) in Jacobian coordinates. ...
0
votes
1answer
55 views

Encrypt a Zip File with Caesar Cipher

I'm trying to understand, why the Filesize of a Caesar Cipher encrypted foo.txt.zip File is smaller than a Caesar cipher encrypted foo.txt File. For example: Foo.txt size: 90bytes foo.txt.Caesar.enc ...
3
votes
1answer
67 views

Where did the SHAKEs come from in SHA3?

Where did SHAKE128 and SHAKE256 originate from? I am trying to find them in the original Keccak documentation but can't find them. Is it some special mode of Keccak referenced in the documentation? ...
-1
votes
1answer
167 views

Is it possible to find plaintext from ciphertext if (n) and (a) are known for RSA?

I have a couple of questions pertaining to a RSA problem. I need to decipher some ciphertext and find out what the original plaintext was. Modulus: $n = 2537$ and exponent: $a = 11$ Encrypting ...
-3
votes
0answers
68 views

Rijndael performance

I have written the routines Rijndael 128-Bit ENC/DEC and KeyExpand. In bit sliced SSE2, and from his OPS would like to know its performance. The results are as follows: ENC: SubBytes&Shiftrows ...
3
votes
1answer
289 views

How does MD5 process text which is shorter than 512 bits

MD5 processes a 512-bit block and produces a 128-bit (16 byte) message digest often expressed as 32-digit hexadecimal value For example if I hash the word "how" using MD5 , I get the following hash ...
7
votes
1answer
140 views

How dead is braid based cryptography

Braid groups has drawn the attention of cryptographers for a few years, as a promising platform for post-quantum cryptographic protocols. The security of the proposed schemes mostly relied on ...
-1
votes
0answers
108 views

Do passphrases need to be run through PBKDF2? Almost impossible to brute force? [migrated]

Passphrases normally contain more data then passwords and can provide more entropy. It seems like it would still be hard to brute force a passphrase w/o using PBKDF2, assuming a user didn't select a ...
0
votes
1answer
68 views

Is it possible to distinguish a CRC hash? [closed]

I have a program that generates random combinations of 8 characters including numeric characters and abcdef. I want to know if it is possible to identify which of these are actual CRC hashes and which ...
1
vote
1answer
77 views

Weak key schedule IDEA [on hold]

Why was such a weak key schedule chosen for IDEA? The key schedule of IDEA works like this: Divide the key (128 bit) into 8 round keys, each 16 bit long. This are the first 8 "round" keys (6 keys per ...
3
votes
1answer
322 views

RSA example-calculation: Public Key = Private Key (e = d)

I am a bit confused. I just calculated manually the single steps of RSA for an implementation with small numbers and suddenly $d$ was equal $e$. Please help me understand what I am doing wrong. ...
1
vote
1answer
108 views

Is it possible to demonstrate that md5(x) != x for any x?

I am looking for an easy to follow explanation, if possible, that demonstrates/proves the validity (or not!) of this assertion: for any X, md5(X) != X (being X any string of 32 hex characters)
0
votes
0answers
8 views

Finding all primitive polynomials of a certain degree in $\mathbb{F}_q$ [migrated]

I am writing an algorithm to find all primitive polynomials in $\mathbb{F}_2[X]$ and I found this theorem : If $P(X)$ is a primitive polynomial in $\mathbb{F}_p[X]$ of degree $n$ with root $a$, then ...
1
vote
0answers
28 views

Serpent Cipher 128bits (Example rounds on any plaintext/key)

Is there are any possibility to see trace(example) of Serpent Encryption/Decryption on concrete plaintext/key example, (not code implementation) or at least animation of steps. During reading of ...
0
votes
1answer
34 views

Using C_Sign to create a PKCS7 signature

I am using the PKCS#11 function C_Sign to sign some data. The output I get is just a signature. How do I get it in PKCS#7 format - i.e. ASN1 with signature and certificate (for detached) or ASN1 with ...
8
votes
2answers
6k views

How does a chosen ciphertext attack work, with a simple example?

Can someone please explain - using a simple example - how a chosen ciphertext attack works?
2
votes
3answers
155 views

How do I generate a number for a lottery and later proves its existence

I want to create a lottery that works like this: I choose a secret number A in the range [0:999] and publish an object B. People must try to guess the number A to win. When somebody wins, I want to ...
1
vote
2answers
142 views

How exactly does AES-NI work?

I am looking in to AES-NI which is now supported by many new CPU's and I have read a few papers which states that AES-CBC works faster with AES-NI, but I am unable to understand how exactly AES-NI ...
0
votes
0answers
26 views

Generating a public key certificate with ECDSA params

I have an ECDSA key generated in a HSM and I am able to retrieve it's public key components via the PKCS11 library. I would like to create a public x509 certificate with the public params for the ...
4
votes
1answer
103 views

Security analysis of Spritz?

Recently, a new cipher called Spritz has been released by Ronald L. Rivest and Jacob Schuldt. It should be a "drop-in replacement" for RC4. There are many differences to RC4, Spritz is "spongy" and ...
-1
votes
1answer
70 views

Block Cipher Modes

I have a question here asking the following: Why do block ciphers need the use of blocking modes? To encrypt messages larger than the size of the block. To avoid having the same block ...
1
vote
1answer
97 views

How can I map arbitrary group elements to unique integers without using Hash functions?

Let's say, I have a group $G$ of large prime order $p$. A set $S$ consists of $n$ random elements chosen from $G$. Without using a collision resistant hash function $H$, how can I map elements of $G$ ...
-1
votes
0answers
38 views

how does the order-preserving encryption scheme distribute the buckets?

Recently ,I want to know the order-preserving-encryption scheme(OPES in short).But ,I couldn`t understand how the buckets are distributed,and if the values in my input database are in a small range, ...

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