# All Questions

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### is this possible to use asymmetric encryption schemes as order preserving encryption

Are we able to use order preserving encryption in asymmetric schemes, is this work efficiently. is this secure at any one of the situations
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### How many characters per block in an El Gamal ECC cryptosystem?

Looking for the number of characters that can be encrypted using the The elliptic curve ElGamal cryptosystem of each block, I found these lines. But I cannot understand them: Actually in our case ...
294 views

### Why does rsyncrypto require a public key during decryption?

I recently came across a project called rsyncrypto that sacrifices some security so that you can have rsync-friendly files. My understanding is that it works by generating a symmetric key for each ...
184 views

### What are the differences between the elliptic curve equations?

I think we're all aware of the "classical" Weierstrass (short?) elliptic curve equation: $y^2\equiv x^3 + ax +b \pmod p$. Well known examples of these curves include the NIST's and Brainpool ones. ...
308 views

### How to quickly detect incorrect password in encrypted file without compromising security?

I am developing a software to encrypt/decrypt files/streams using symmetrical encryption algorithm. During encryption phase data wil be compressed and encrypted. When decrypting data, I want to be ...
159 views

### Is MCrypt's 8-bit OFB mode secure?

I just stumbled across a Stack Overflow post which points out that the libmcrypt library (notably used in PHP) implements a somewhat unusual set of block cipher modes: it calls the usual CFB and OFB ...
9k views

### SHA512 faster than SHA256?

I'm getting this strange result that SHA512 is around 50% faster than SHA256. I'm using .net's SHA512Managed and SHA256Managed ...
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### Securely start a client server connection without ssl/tls [closed]

NOTE: Pardon my ignorance of encryption, I learned about these concepts today Going to rephrase this question, but I think I already have fine answers provided. I need to have a block of data ...
348 views

### Where can I learn the basics of AES?

I was tasked with making an expo about AES and its steps, but I still can't grasp it, especially when it comes to "key schedule". Does anyone know some good material to start learning? Or can someone ...
324 views

### How HMAC.Update function works?

I know how standard HMAC(key,msg) function works, and I want to write a Delphi port of HMAC class that implements Update function. The problem is that I don't understand how this Update function works ...
188 views

### What is difference between Cryptographic Transformation, Encryption and Hash? [duplicate]

I read in a book that: let $f(K,R)$ is cryptographic transformation of $R$ using $K$, $K\{R\}$ means $R$ is encrypted using $K$ and $h\{R\}$ is the hash of $R$ and then the example follows. I want to ...
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### how does https key get shared?

I am only a beginner and doesn't know much about https. I have heard that they uses somekind of a key and is shared between them. If an attacker wishes to attack could he be able to capturebthe key ...
140 views

### Unbreakable code and mathematical impossibility

Is an unbreakable code mathematically possible , considering a code with finite number of characters but has infinite combinations , using brute force is it not compulsory that the correct code be ...
158 views

### My own encryption algorithm - if someone can brake [closed]

I wrote recently my own encryption algorithm. I want to test it so, since I know that here are a lot of professionals, I will write here some encrypted text and if someone is able to decrypt it please ...
120 views

### AES encryption algorithm [closed]

What is the amount of decrease in the probability of decrypting a data encrypted using an AES algorithm? (That is by introducing each round out of ten whole rounds, how the probability of decryption ...
121 views

### Generic name for (?hash) functions of form $\{0,1\}^n \rightarrow \{0,1\}^{poly(n)}$

Consider a function $$f: \{0,1\}^n \rightarrow \{0,1\}^{poly(n)}$$ with the following properties: hard to invert, i.e. given $f(x)$, hard to find $x$ hard to find a collision, i.e given $f(x)$, ...
82 views

### Period of pseudo random sequence generated from (5, 2, 0) LFSR

I was reading about the Linear Feedback Shift Registers and I am confused about the technique to find the period of a primitive polynomial. Consider the polynomial $x^5 + x^2 + 1$. As this is a ...
82 views

### Signature scheme doesn't seem to hold

I can't seem to verify the signature scheme described below. Key Generation Public Key: $$y_1=g^{a_1}y^{a_2} \pmod p$$ $$y_2=g^{b_1}y^{b_2} \pmod p$$ $g$ denotes a generator of $Z_p^*$ and $y$ ...
111 views

### AES process candidates implementations and usages

There were fifteen candidates in the AES selection and I suppose that Rijndael wasn't the single good algorithm. I know that Camellia is an evolution of E2 candidate and can be used as symetric ...
62 views

### Compression in Symmetric-Encryption?

When using symmetric encryption is it important to compress the data first? I think that compression will make data look "more random" and this might help the ciphertext be harder to crack but I am ...
47 views

### Digital signature in a group chat scenario?

I understand that RSA is great for 1-to-1 digital signature. In the group chat of N people, other than storing and maintaining N public keys, is there a simpler way of authenticating each and everyone ...
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### Fortuna: why are source ID and data length added together with entropy data into the pools

Section 9.5.6 of Cryptography Engineering states that The concatenation [of source number, length of data, and data itself] is then appended to the pool. Why are we including source number and ...
1k views

### Purpose of outer key in HMAC

From what I know, the HMAC constructions has two strength: It's resistant to length extensions Since the key is consumed before the message, the attacker does not know the initial state, preventing ...
146 views

### security in format preserving encryption

In format preserving encryption an attacker knows the format and data type of the plain text. The format of the plain text and cipher text are same. usually cipher text are unreadable form. then how ...
212 views

### Encryption of exe file

I recently started learning cryptography. I have learned some basic stuff. I'm also started learning about pc security, so I was wondering how do hackers use cryptography for bypassing antivirus ...
191 views

### Meaning of entropy of a bitstring in NIST SP 800 - 90A

From NIST SP 800 - 90A from January 2012 (see http://csrc.nist.gov/publications/nistpubs/800-90A/SP800-90A.pdf), page 6: For the purposes of this Recommendation, an n-bit string is said to have ...
448 views

### Supersingular Isogeny Key Exchange Software [closed]

Are there any optimised implementations of the Supersingular Isogeny Key Exchange by Defeo, Jao, and Plut. It seems like this would be a great drop-in replacement for Diffie-Hellman in both OpenSSL ...
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### Blinding value of particular form

I'm working with an implementation that creates a blinding value for RW signatures with the following C++ code: ...
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### Why does UMAC encrypt the output of universal hash function?

UMAC uses a key to choose a random hash function from a family of universal hash functions. The value of the hash function is always encrypted using yet another key, and the resulting ciphertext ...
87 views

### Safe way to generate different encrypted output from the “same” plaintext

Imagine I want to send imaginary defcon levels to another party over the internet. I know there are good protocols for this like SSL, but lets say I only have a blackbox tool where I can input an AES ...
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### Is DES slow in hardware or only in software?

I have been reading that DES is slow. Is it only slow in software or slow overall? Also, as far as Triple DES being slow is concerned, is double AES with two 128 bit keys slower than single AES with ...
4k views

### simple algorithm to encrypt/decrypt a text file

I need to write a first program in one language that saves data in a text file, and write a second program in a second language to decrypt that file. The two languages in question don't include any ...
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### Cryptanalysis and Copying encrypted volumes

I just recently concerned myself with cryptography due to Snowden's revelations and there are a few things I cannot really wrap my head around but maybe you can help me with that. I am not a ...
212 views

### Is there a cryptographic algorithm which is immune to side channel attacks?

Is there any cryptographic algorithm immune to side channel attacks based on scan chain? In VLSI point of view.