3
votes
1answer
267 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
211 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
44 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
254 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 ...
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
69 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
74 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
141 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 ...
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
344 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
109 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
36 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
36 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
143 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 ...
5
votes
1answer
104 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
71 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, ...
8
votes
2answers
279 views

What is the sign bit for in Feige-Fiat-Shamir?

The Feige-Fiat-Shamir identity scheme is based on a ZKP assuming that square roots are "hard" modulo an integer of unknown factorization. The "parallel version" of this protocol includes a "sign bit" ...
1
vote
1answer
51 views

RFC3447 OBJECT IDENTIFIER semantic

http://tools.ietf.org/html/rfc3447#appendix-B.1 ...
1
vote
2answers
60 views

Is .NET DESCryptoServiceProvider secure in this case?

I have the following piece of .NET code (see below). I know that DES is not quite secure, I saw that MSDN does not recommend using DES, only for compatibility with legacy programs. I also saw that ...
2
votes
1answer
201 views

Do Export Restrictions Still Apply To The Key Length of RC4?

I've just read a paper from 2004 which stated that the RC4 encryption algorithm was restricted to a 40 bit key size when exported from the USA; however the reference for this information (Applied ...
0
votes
0answers
61 views

Bit level permutation

Could anyone explain how secure is bit level permutation? What is the most serious threat against the security of this kind of cipher? Thank you
1
vote
1answer
77 views

Breaking RSA moduli

Let suppose that the sizes of factors $p$ and $q$ are $b$ bits. We construct two RSA numbers $n$, $n'$ of same sizes. Can we say that the duration to break these two numbers is two times the duration ...
0
votes
1answer
28 views

What is meaning of “Decipher the rest of the message by deducing additional words”?

I have an assignment in cryptography. I am not asking here answer, but meaning of question. This is a question : 2.4 The following ciphertext was generated using a simple substitution algorithm. ...
2
votes
3answers
158 views

Does this guarantee a unique 32 bit Hash?

I came across some source code that loosely does the below in order to achieve a 32 bit hash. The input string is passed through MD5 to get 16 bytes Hash (as usual). Then the 16 bytes are split into ...
0
votes
2answers
61 views

I'm using AES-CTR as a CSPRNG - Do I need an IV?

I'm using AES128-CTR for generating pseudo-random values, which is considered secure for up to 1MB (at least from what I've read). I simply encrypt a 128-bit little-endian counter, starting from 0. ...
0
votes
1answer
13 views

FEAL-4 Fk Function 4 Rounds

As I understood in FEAL-4 it needs 4 pair of round keys. Which means that we need to launch Fk function 4 times, but the problem occures on the 2nd round. At first round we have original 64 bits key ...
0
votes
0answers
42 views

how to find key matrix in hill cipher

I want to solve this problem but there are 3 known plaintext-ciphertext pairs. The key of Hill cipher is a 3*3 matrix as k=[k1,k2,3; k4,k5,k6; k7,k8,k9] where the unknown ...
0
votes
1answer
154 views

Fast AES-128 on 32 bits encryption

Suppose in AES-128, there are $5$ tables, namely Te0, Te1, Te2, Te3, Te0 which help in fast encryption on $32$ bits CPU. Each table contains 256 numbers, where each number is $4$ bytes. Te4's ...
8
votes
2answers
673 views

Is the 64-bit blocksize a fatal issue when encrypting TBs of data with Blowfish CBC?

Crashplan uses 448-bit Blowfish to encrypt the data you send them. The mode used is CBC, keys are multiple use, and IVs are generated with SecureRandom from JCE. Keys are not derived from the ...
-1
votes
1answer
154 views

RSA given q, p and e?

I am given the q, p, and e values for an RSA key, along with an encrypted message. Here are ...
2
votes
1answer
55 views

Can adding nonces make challenge response authentications weaker?

In a custom protocol we want to replace an aged tiger32 based challenge response authentication. I suggested that we use something existing, so threw HMAC into the room. As per wikipedia it works as: ...
0
votes
0answers
55 views

side channel attacks on AES

Say you have a web application that's performing AES encryption. What sorts of side channel attacks should one keep an eye out for? Timing attacks affect RSA more than symmetric ciphers in-so-far as ...
6
votes
3answers
217 views

Is there a string that's hash is equal to itself?

I was wondering if there's any string that has a hash equal to itself, so that – when using any (none specific) hash function – the hash would be equal to that string? so that: ...
-1
votes
0answers
31 views

Guarantee signed data set time interval

I have some data data which is created using some hardware measurements. I now need to guarantee somehow that the data was created in a configurable interval of time. My idea was to use a central ...
0
votes
1answer
48 views

Session based AES with random key and static salt

I'm currently using aes to encrypt/decrypt messages to and from a web service. When the user establishes a session he sends a random generated secret via rsa public key. This secret is used to ...
0
votes
3answers
179 views

Are hash functions chaotic?

I'm looking into "bitcoin like" mining processes. Say a security process uses a hash of data as proof that the data was known at some point in time. From what I understand, hash functions are ...
1
vote
1answer
39 views

Linear transformation proof

Ok, so I have this question and I honestly have no idea how to prove it. I know that the function is linear and I know it works for every possible combination, I just don't know how to prove it in an ...
3
votes
2answers
320 views

Why not use an algorithm's code rather than data itself for one time pads?

Instead of using actual data for one time pads, what would be different if the code for an algorithm was exchanged so that to acquire the pad one would execute the algorithm and use its output? Why ...
0
votes
0answers
39 views

Need help solving message encrypted on an Enigma machine?

So basically I'm in a class an one problem we were given a while ago was one involving an enigma machine and a few messages. I do not have any idea of how to approach it, and I really need help. The ...

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