Tagged Questions

Encryption is the process of transforming plaintext using a cipher into ciphertext to make it unreadable to anyone except those possessing the key. Decryption is the process of transforming that ciphertext back into plaintext, using the key.

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16 views

Show that the equal difference property exits for a modified DES encryption system

My cryptology professor gave us this problem on a past homework assignment and I only managed to get one of the 3 parts correct. Needless to say, I want to know how to do the other two parts as well. ...
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1answer
22 views

Simplest code for 64-bit block RSA-like encryption/decryption and key generation

Looking for the simplest code in C. Need a set of functions that will first generate a public/private 64-bit key pair, and then the function to code/decode a given 64-bit block, no built-in checksum ...
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0answers
23 views

Type of cipher used where ciphertext has no discernible pattern, spaces. Type?

What type of cipher could give ciphertext where for example random ASCII chars between say F-z (symbols and numerals inclusive), but with only a few spaces? Frequency of chars shows some similarities ...
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0answers
10 views

?, software/hardware solution(s) for encrypt/decrypt of NAS(s)/SAN(s) that vary in size. LUNs are 4tb+ [migrated]

well hello newbie..first of...with truecrypt & bitlocker totally out of the question (the security issues), what software solution would you recommended to be used to encrypt/decrypt (on the fly ...
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0answers
35 views

How to add our created session encryption algorithm to (major) browser using OpenSSL [migrated]

I am new to OpenSSL and have theoretical information in SSL protocol . I have task to create a certificate who uses RSA algorithm for symmetric session key exchange and use my own my encryption ...
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39 views

Public key encryption without ciphertext expansion

Say I have a database column that is defined as VARCHAR(255) that stores names. I can assume that names can be up to 255 chars. I need a public key encryption so that I can replace names with their ...
1
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1answer
67 views

How can a good pseudo-random number genarator be made?

I am trying to make a pseudo-random number genarator so that I can use it in a synchronous stream cipher for encrypting plain text. I want it to genarate numbers which are as random as possible. Can ...
1
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1answer
76 views

Why does openssl use SHA1 in ECC when I use secp384r1 curve

I need a small clarification that why openssl using SHA1 in ECC when I am using secp384r1 curve, but in rfc they are saying we should use SHA2. Thing here is am using nanoECC in my DTLS, nanoECC ...
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2answers
102 views

Encryption algorithm designed to be easy to decrypt by machine but impractical to decrypt by hand

I am looking for - or considering the design of a new - encryption algorithm that does not use variable keys, such that it is easy for a computer to encrypt and decrypt any message regardless of its ...
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1answer
47 views

rsa public and private keys

I have a question about RSA key generation: this is a simple rsa algorithm: Choose p = 3 and q = 11 Compute n = p * q = 3 * 11 = 33 Compute ?(n) = (p - 1) * (q - 1) = 2 * 10 = 20 Choose e such that 1 ...
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1answer
60 views

Are there any many to one encryption frameworks available?

I am reasonably new to the cryptography. For my use-case I need a method where in I would need a receiver to accept encrypted messages from a range of senders (each having their own, say, public key). ...
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1answer
54 views

Client-server communication

The base scenario goes as follows: A program stores some user's confidential data encrypted on their disk. The user is most probably clueless and the disk might get stolen, but these are the classical ...
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0answers
123 views

Cryptographic Dilemma [on hold]

I'm reading an article where they are talking about 'the Cryptographic Dilemma. Is there one universal dilemma in cryptography? I can think of a few, like computation time vs. crackability. The ...
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1answer
41 views

Cipher Alphabet [closed]

Present the first 50 characters of the plaintext of the ciphertext below. NPKLMBAMMAKLNFKCSDABAUADMRMADBAMMAKVFKGSDGVRPEREFBBAEMPUABX PDEBQGASBBMVFLPWBAMMAKLFNMRASBIRSTAMMRAEFBQCDLPDIFKMSLGPSOK ...
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1answer
78 views

A one way Function provably reversible at N applications with the same seed?

I'm looking for a function that is generally one way from some secret $F(s, A) \rightarrow Y$, where $A$ is known, $Y$ is produced (also known), and $s$ is kept secret. But whose repeated application ...
2
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1answer
51 views

How secure is a lagged fibonacci sequence for encrypting brief messages?

Say I start with a 26-letter keyword and convert the letters into 26 integers (A=0, B=1...Z=25) nr[0] to nr[25]. Then I create a stream, nr[26] onwards, with a lagged fibonacci sequence where nr[n]= ...
5
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1answer
393 views

What do you call one time pad where pseudo-random numbers are used?

What is the encryption method called when pseudo-random numbers are used instead of true random numbers?
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2answers
56 views

Large file validation on an embedded system through hash and encryption

As a preface, I have to say that I am a noob in this area. Having said that, I will ask the question. I have a situation where I need to validate and protect against tampering a handful of large ...
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2answers
128 views

Operation which needs much computing power to be created, but just a little to be solved?

Does somebody know a cryptographic/mathematic operation, that needs much computing power to be "encrypted"/"created" but doesn't need much power to be "decrypted"/"solved"?
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3answers
105 views

Format Preserving Encryption for 32 or 64 bit plaintext values

I am looking for a Format Preserving Encryption implementation to apply to either a 32-bit or a 64-bit integer. It looks like AES/FFX mode is just what I need in terms of established security ...
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1answer
39 views

Convert message to polynomial NTRU

How to make a message into a polynomial? I saw many answers to this question and yes, i know that here are some questions. But i did not get it. I think that i am making some mistakes. I took a word ...
0
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1answer
56 views

Prepending random data to encrypted file

If random data is prepended to a file encrypted with GNUPG's symmetric encryption, how may an attacker find out if the input file is deliberately corrupted or the passphrase is wrong? If it is not ...
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0answers
17 views

Verify signed file using GPG by passing in signature hosted online rather than stored locally (i.e. in keyring)? [migrated]

Is it possible to pass the URL of a GnuPG signature when executing a verify query against a signed file? For example, instead of: gpg --verify file.txt Is there ...
3
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1answer
153 views

ZIP 2.0 encryption bruteforce attack

I have an old sourcecode backup from my DOS days stored in a ZIP 2.0 encrypted archive, but I lost the password. The password was written on a paper slip, but I remember that it consisted of 30+ ...
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1answer
61 views

problem with “one time pad” [closed]

I am a french student and I read the post on the forums (How does one attack a two-time pad (i.e. one time pad with key reuse)?). I need your help if possible. I 'm 11 encrypted messages , all ...
2
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1answer
73 views

Implementation of garbled circuits using RSA

I was just reading these notes on garbled (Yao) circuits and I just stuck trying to figure out how an implementation of Table 1 would work using RSA encryption. In RSA the public key is (n,e). So for ...
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1answer
37 views

blowfish ecb with openssl doesn't give the expected result

I do the following via the Linux CLI: ...
0
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1answer
105 views

Encrypting twice with different modes?

I was using a SOCKS5 proxy today (tunneled through SSH) and I began to wonder what the effect of encrypting twice (TLS over encrypted SOCKS5 in this case) would have on the security of the transmitted ...
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1answer
78 views

Cryptography system that limits the length of the encypted message

I have two devices which communicate via sms. This communication should now be encrypted. The devices can only send messages with the lenght of 160 characters. So i am looking for an encryption ...
2
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1answer
46 views

Use of ElGamal encryption for signature generation

If RSA (textbook RSA that is) generates a digital signature by using the sender's private key, couldn't any cryptosystem (the only two that come to mind are RSA and ElGamal) capable of asymmetric ...
2
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1answer
68 views

Encrypted read-only message queue

I'm creating a prototype for a messaging queue with some custom logic (can't re-use any existing solution). One requirement is to have all messages encrypted. There are three classes of nodes ...
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1answer
52 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 $n \times n$ matrix, again ...
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46 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
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1answer
60 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 ...
4
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1answer
95 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 ...
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1answer
45 views

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

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 ...
0
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1answer
59 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 ...
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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 ...
2
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1answer
223 views

Serpent 256bit key wrong round keys

Assume that we have this 256bit key: 15FC0D48 D7F8199C BE399183 4D96F327 10000000 00000000 00000000 On first 0-7 keys we can't apply formula wi=(wi-8 xor wi-5 xor wi-3 xor wi-1 xor phi xor ...
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1answer
14 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
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1answer
157 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 ...
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16 views

How can one recover a message from the RSA system? [duplicate]

Consider an RSA system with n=143, e1=7 and e2=17. Suppose the same message m was sent to the two users above and the attacker observed the ciphertext c1=42 and c2=9. Show how the attacker can recover ...
1
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1answer
59 views

Number of keys for a monoalphabetic cipher

My teacher stated that… The number of possible keys (E) in a monoalphabetic cipher is $26$! My thinking: Every letter in the alphabet can be $25$ different letters hence it the number of ...
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2answers
773 views

How is XOR used for encryption?

I am a programmer, so when I hear XOR, I think about the bitwise operator (e.g. 0110 ^ 1110 = 1000). The mention of "XOR" comes ...
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0answers
48 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 ...
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0answers
42 views

Need to choose an ecnryption method [closed]

I've got an homework to implement an encryption algorithm (I can choose what), now we didn't learn about encryptions yet, I guess you can call it pre-class homework or something, I know what is ...
0
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1answer
72 views

A variant of Shamir secret sharing

Suppose implement the Shamir secret sharing as following: we select a degree $d$ polynomial $P$ with a zero coefficient of 0, and all other coefficents selected randomly from $Z_p$; and to this ...
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0answers
34 views

Is Attribute based encryption sub-class of Identity based encryption [duplicate]

I have a basic question related to Identity and Attribute based encryption. Construction of IBE scheme was first shown by Boneh et al. in 2001 and I think in 2004 Sahai and Waters introduced ...
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1answer
161 views

Homomorphic encryption based on XOR

Consider the values $a$ and $b$ are encrypted as $c_1=(a \oplus D)$ and $c_2=(b \oplus D)$. My question is: can we derive $b+a$ from any combination of $c_1$ and $c_2$? Note: I admit that the ...
2
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3answers
157 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 ...