0
votes
1answer
86 views

Public key encryption [duplicate]

I am not getting whole idea behind Public Key Encryption technique. As according to fact, public key encryption method uses two keys a public key known to everyone private key known only to recipient ...
2
votes
1answer
293 views

Deduplication: Encrypting the SHA-256 hash of a file chunk

I'm designing a data storage system that should be both able to deduplicate data that share the same encryption key, and be reasonably secure. I know that this kind of encryption quality can be ...
2
votes
1answer
305 views

Sophie Germain primes and safe primes

I am trying to find a list or table of safe prime numbers i.e. the ones that are based on the Sophie Germain primes i.e. $N = 2p + 1$ where $p$ is also prime. All I found till now is this database. ...
1
vote
3answers
122 views

Loss of data due to encryption

Could any kind of encryption method (AES, etc.) lead to data loss like in lossy compression? I'm interested if data (lossy compressed, lossless compressed, uncompressed) that is encrypted and ...
0
votes
1answer
96 views

Interested in learning cryptography [duplicate]

I'm interested in learning cryptography outside the university(studying civil engineering). I was always interested in computer sciences and programing and in mathematics. I always try to program ...
4
votes
2answers
264 views

Share encrypted files without giving master key

Imagine I have four files I want to encrypt. I have master key, and from that master key I derive four keys, one for each file: ...
3
votes
2answers
394 views

Encryption for a short packet size

I have an 8051 microcontroller with a radio that can send packets with up to 32 bytes and I want to have the messages encrypted. It is a sensor network so I really only want to send one packet per ...
2
votes
0answers
248 views

Difference between statistical PRNG and cryptographic PRNG? [duplicate]

What's the difference between a statistical pseudorandom number generator (PRNG) and a cryptographic-strength PRNG? I've seen a lot of PRNGs that are proposed for statistical uses -- e.g., ...
1
vote
2answers
153 views

NTRU key generation

I've been experimenting with an NTRU open-source C implementation here I've noticed something (potentionally) strange with a certain set of params: NTRU_EES1087EP2 (defined here). When generating ...
-2
votes
1answer
310 views

How many bits of entropy would I get from 300 coin tosses? [closed]

Bonus question, what is the formula to calculate this?
1
vote
2answers
145 views

What is the keyspace of ROT-13?

Today I was having a discussion with my cryptography lecturer about the keyspace of a ROT-13 cipher. He argues that the keyspace is 0 because it doesn't have a key. Could anyone explain to me why the ...
0
votes
1answer
101 views

Is adaptive security the same as full security?

This question contains a great answer about adaptive security, but I haven't yet found a proper definition what full security is. Does a stronger security than adaptive security exist or are the two ...
3
votes
5answers
2k views

Why is the private key generated first in public key crypto?

I'm still new to public key crypto. I'm trying to understand how it is that the private key is generated first in public key crypto? I would have expected the private and public key to be generated at ...
3
votes
3answers
352 views

How to roll my own hardware RNG?

I am considering building a hardware RNG myself using cheap parts. Is this a good idea and safe enough? Random sources: amplified Zener noise from one randomly chosen ...
0
votes
2answers
94 views

Analyzing security flaws of cipher

I know using homebrew encryption can be very dangerous as it is very likely to have many flaws in its design. The following concept is just for learning purpose in case anybody is getting red flags ...
0
votes
2answers
120 views

Is my method symmetric encryption?

To obfuscate data I made up this method on the spot without planning since the goal wasn't real encryption. At first I though this cannot be real encryption but after revisiting the code and reading ...
1
vote
1answer
263 views

Performance bottlenecks in Paillier encryption

I'm implementing Paillier encryption and I'd like some recommendations about improving its performance. Firstly, I have to note the following: I have already set g=1+n to get rid of one ...
1
vote
1answer
157 views

Transforming a key into a seed with the most entropy

I'm making a very simple encrypter in C# which is basically a Stream cipher. The user enters a key(password), converted to a seed for a pseudo-random generator, and the pseudo-random generator ...
0
votes
1answer
401 views

How to calculate AES logarithm table?

I would like to know how to find multiplicative inverses in $\mathrm{GF}(2^8)$. I know how to multiply two elements of $\mathrm{GF}(2^8)$ (for example, I know that ...
1
vote
2answers
192 views

What is a good way to demonstrate elliptic curve cryptography?

For school (high school) I am writing an essay on elliptic curve cryptography. The assignment needs to include a practical part, so I decided to write a Python class for elliptic curves. This class is ...
9
votes
1answer
1k views

How does ECDH arrive on a shared secret?

I read a brilliant, three part article on Elliptic Curve cryptography (one, two, three). It was able to explain Elliptic Curves to me in a way that didn't require a math degree to understand. The ...
2
votes
1answer
193 views

Why are there no MACs inspired by block cipher modes other than CBC and CFB?

I've been studying message authentication codes and I was wondering why a MAC can only be produced with AES in CBC and CFB mode and why not the other modes such as ECB, OFB and counter. Why are CBC ...
-1
votes
1answer
167 views

How are calculated numbers in AES S-box? [duplicate]

My question is how to calculate the 0x02 value of AES S-Box? I followed this explanation, but my answer is not correct. 0x02 is ...
0
votes
0answers
220 views

RSA - Why should we sign hash rather than raw content? [duplicate]

Apart from obvious performance considerations, is there any mathematical or crypto reasons that imply that we sign a hash rather than a raw content ? I read that it was because the hash must fit in ...
0
votes
1answer
215 views

C# implementation of curve25519 to ed25519 conversions [closed]

WRT the selected answer here: Can curve25519 keys be used with ed25519 keys? Is there any c# implementation of this or equivalent? Thanks.
3
votes
0answers
120 views

Relations between RSA and DLOG, factoring and DLOG

Definition: (The generalized Diffie-Hellman problem) Let $n=pq$ for two large primes $p,q$. Given $x, x^a, x^b,n$, find $x^{ab}\pmod{n}$. (1) Is there a known reduction from the GDH problem ...
1
vote
1answer
462 views

Finding discrete logarithm with baby-step-giant-step algorithm

I am trying to use the Baby Step Giant Step algorithm to find discrete logarithm in: $$a^x= B \pmod p$$ with using BSGS: $$x = im+j$$ $$a^j = B a^{-im}$$ where $m = \sqrt{p}$ Wikipedia says: ...
2
votes
1answer
81 views

Post processing of AAD and len A||C in a hardware AES GCM implementation

I'm new to GCM and I need to implement it in hardware, using FPGA. The data bus is 640 bits, so I will use 5 adder/multiplier blocks in parallel. The message size and AAD size are constant. My design ...
0
votes
1answer
82 views

Adding a Password Hash (key derivation) function to existing password storage solution

As always we are trying to improve password storage; before just adding new ways of storing our password we need to define what threats we will mitigate by adding in a new way to store our password. ...
3
votes
1answer
368 views

Plaintext XOR'd with keylength-shifted plaintext

While solving a (easy...) Project Euler cipher problem this week I repeatedly saw instructions for breaking ciphers after identifying the keylength as: 'shift the ciphertext by that key length and ...
0
votes
4answers
266 views

what is it called when encrypt('a') + encrypt('a') == encrypt('aa')?

So normally if you do encrypt('a') twice in a row you'll get the same result. But sometimes (as is the case in SSH) this is not desirable. You want encrypt('a') + encrypt('a') == encrypt('aa'). What ...
0
votes
1answer
144 views

How exactly to extract information base 10 from a PGP RSA key pair?

I think I understand the mathematics of RSA ok. I'm not so computer savvy though. How, exactly, can I extract $n$, $e$, $d$, $p$ and $q$ from a PGP RSA public key pair? Is there like a converter ...
3
votes
2answers
221 views

Smart Card - Entropy during on-board public key generation

I know that some (advanced) smart cards or tokens allow generating key pair directly on the device, but I wonder how the card can gather entropy during the process. Any idea ?
1
vote
2answers
233 views

(Re-)Using deterministic IV in CTR mode / How to: deterministic AES

I am aware of the requirement of an IV to be unique in CTR mode (Why must IV/key-pairs not be reused in CTR mode?). However I wonder if I can use an IV depending on the plaintext deterministically. ...
0
votes
1answer
122 views

Size of a MAC for a quickly checked message?

Let suppose that we have to check a message that was written one second ago. The message is discarded immediately after having being checked. What "minimal" size for such a MAC is secure ? Thank you. ...
0
votes
1answer
85 views

If I know the salt, can I decrypt the commitment?

Say, I salt my key(K) with y. So, my new Key is K' = Salt(K+y). Now, Alice sends commitment = E[K',M] to Bob. Bob knows the salt(y), but not K nor K'. Can Bob decrypt the message?
1
vote
2answers
232 views

Are there cryptographic hash functions which do not have any collisions?

I've been studying digital signatures and hash functions recently, and I was wondering: Do hash functions exist which will never produce collisions?
1
vote
1answer
52 views

Is AES_CMAC specified to double ciphered zeroes during initialization?

Reading the SIV RFC https://tools.ietf.org/html/rfc5297#page-9, I found that the S2V function starts by calculating the MAC of a "zero" block, doubles it and then XORs further data to the result. Now ...
0
votes
2answers
91 views

Is BBS used for generation of keys for any modem cryptosystem?

Is there any (current) cryptosystem or digital signature or cryptographic primitive that uses the BBS PRG in order to generate its secret keys?
0
votes
1answer
82 views

Asymmetric sign in public enviroment

I have RTS game, where all players run game and server just relays messages. Game can generate and store text file on player pc. I want to allow some players to be moderators, so I need to sign or ...
0
votes
2answers
58 views

How to use HMAC for authenticating multiple messages

The standard HMAC function, $H(K, m)$, authenticates a single message $m$. Instead, I'd like to authenticate 2 messages, like this: $$H'(K, m_1, m_2)$$ The simplest solution, $H(K, m_1||m_2)$, ...
0
votes
1answer
98 views

Is it possible to decrypt this message with partially known data? [closed]

The following highlighted text must contains 547a5e0e008be33730158d63ce844e67 data. I don't know about encryption method and key. Is it possible to decrypt it? ...
-3
votes
1answer
299 views

can anyone give the java code to encrypt files using paillier [closed]

I want to implement encryption on personal files using paillier encryption. Is it possible to encrypt files using this encryption..
1
vote
0answers
55 views

emulating progressive encryption with RC4 / OpenSSL

PHP's OpenSSL bindings do not support progressive encryption by default. ie. if you do ...
6
votes
5answers
5k views

What is the SSL private key file format?

I was researching about how to encrypt with RSA. I understood everything but not the format of the private keys. In the phpseclib (RSA in PHP), you can import your private key (private.key format) ...
2
votes
1answer
273 views

Discrete logarithm modulo a smooth number

I am solving the discrete logarithm problem modulo $N$. $N$ is a composite number, I found its factors — lots of small primes and two big primes ($> 2^{50}$). Does the factorization of $N$ somehow ...
2
votes
1answer
160 views

Attribute-based broadcast encryption with respect to ABE

What is the exact difference between attribute-based encryption (ABE) and attribute-based broadcast encryption (ABBE)? Is ABBE equivalent to broadcast encryption on top of ABE?
3
votes
2answers
921 views

PRNG determinism (and java.security.SecureRandom)

Looking at getDefaultPRNG() in java.security.SecureRandom makes me very unsure about how to use it. On my desktop, it uses sun.security.provider.NativePRNG, which reads from ...
1
vote
1answer
272 views

Can we quantify strength of encryption scheme ?

Was wondering if we have any (or can we come up with) "units" for strength of encryption like in Physics. Most of our comparative analysis of encryption schemes are based on number of S boxes or ...
0
votes
2answers
169 views

Is the DES F-function injective for a given subkey?

Is it possible for two different half-block inputs to the DES F-function, with the same round subkey, to produce the same output? That is, if we feed two different half-block inputs $b_1$ and $b_2$ ...

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