0
votes
1answer
109 views

security proof in pairing based cryptography

Let : $G_{0}$ and $G_{1}$ be two multiplicative cyclic groups of prime order $p$. $g$ is a generator of $G_{0}$ and $e$ is a bilinear map, $e : G0 Γ— G0 β†’ G1.$ $𝐢_{1} = 𝑔^{𝛽𝑠_{1}} $, $ 𝐢_{2} = ...
0
votes
1answer
24 views

How openssl padding for AES cfb IV?

From a few documents I have read and a few questions about padding here, I think if I passed a encrypted text fewer than BLOCK SIZE, openssl would pad it per PKCS7. And use that padded encrypted text ...
1
vote
1answer
59 views

Special case of format-preserving encryption

Is there encryption algorithm with the following properties? We always have plaintext in natural language, and the produced ciphertext is also in natural language.
-1
votes
0answers
23 views

RSA : Is finding Public key given Private key as hard as finding Private key given Public key? [duplicate]

The question is quite straightforward : In RSA, is finding Public key given Private key is as hard as finding Private key given Public key? If no, can you explain why?
2
votes
1answer
81 views

What does signed fixed window method mean in ECC?

I am studying (sliding) window method in Elliptic Curve Cryptography (ECC) but I am confused by the term, signed fixed window method. By the way term is used in a research paper and not in the book ...
0
votes
1answer
43 views

Encrypt file name

I'm looking to encrypt (rename) mutiple files name based on a passphrase. Currently the passphrase would be numeric but I can change that to something else if required. I would like to be able to ...
1
vote
2answers
265 views

Is ECB mode safe to use with RSA encryption? [duplicate]

Firstly, bear with me, I'm relatively new to cryptography. In a recent static analysis scan of our application, one of the findings complained that we are using ECB: A mode of operation of a block ...
0
votes
0answers
63 views

How do I prove IND-CPA security of RSA-OAEP?

How do I prove that RSA-OAEP is IND-CPA secure? It would be very good to show how to prove it formally, but an informal proof would also be enough. Because of the random number in RSA-OAEP, RSA gets ...
2
votes
1answer
58 views

Optimal bandwidth cost for Oblivious RAM

Goldreich and Ostrovsky show that any ORAM algorithm must have bandwidth cost $\Omega(logN)$, where $N$ is the total number of blocks outsourced. This is in Theorem C of this paper. But they didn't ...
0
votes
0answers
41 views

trying to get calculator and RSA calculatin does not make sense [duplicate]

got two question, I am novice in the area of crypto and currently in big learning curve. From crypto book I am going over with, I see the RSA algorithm example as follows: it chose two rand #-s: ...
0
votes
1answer
76 views

where can i learn the basics of AES?

i was tasked with making an expo about AES and its steps, but i still cant grasp it, especially when it comes to "key schedule". anyone knows some good material to start learning? or someone can give ...
0
votes
0answers
19 views

RFC 5297 implementation [duplicate]

I am looking for an implementation of RFC 5297 algorithm using javascript. I would like to see how to wrap a key on client side web browser, like Mozilla's fxa-auth-client (That uses a xor to wrap) ...
0
votes
0answers
27 views

Can I submit an encrypted message to see if its breakable here? [migrated]

For some reason I have been thinking a lot about encryption lately. I'm a CS major, but an encryption novice. The skeptic in me feels making a code that uses a fairly simple algorithm would be a lot ...
0
votes
0answers
63 views

Why is it a bad idea to use Diffie-Hellman with a prime such that $p - 1$ is smooth?

I recently stumbled upon another question in which somebody menitoned that using custom primes for DH is safe if you keep in mind, that $p-1$ should not be a smooth number. Why is that?
1
vote
1answer
58 views

How to decrypt unusual Many Time Pad

How does one decrypt the many time pad: ($R$ is a random string, $C$ is ciphertext, $P$ is plaintext) $R_0 \oplus R_1 = C_0$ $R_2 \oplus R_1 = C_1$ $P_0 \oplus R_1 = C_2$ assuming that $R_n$ are ...
2
votes
0answers
107 views

Simplicity and precision in cryptography papers

I know a PhD student who recently had his paper on applied cryptography rejected because one the reviewers claimed that it was "the solution was too simple and the notation used was more than ...
2
votes
0answers
58 views

Energy necessary for brute-forcing or decryption

I am trying to understand how the physical limits of computation apply to crytography, and came up with the scenario below as a sort of gedanken. I would be grateful to see how others answer it. ...
0
votes
0answers
42 views

Decypting a Stream Cipher

I am trying to decrypt a stream cipher. I know what the first word of the message is when decrypted but I am unsure how to decrpyt the rest of the message. I know what the first word is because I ...
1
vote
1answer
54 views

Clefia Vs AES 128 bit

I am running a comparison between Clefia (Lightweight cipher from Sony Corporation which is a standard now http://www.sony.net/Products/cryptography/clefia/standard/index.html) and AES 128 bit. The ...
1
vote
1answer
74 views

Format preserving encryption FFX

In FFX mode the format of the ciphertext is same as plaintext. How does it ensure data integrity and authentication? Is there any bit flip attack in FFX mode? Is it malleable?
1
vote
1answer
52 views

SipHash - 64 bit (second) preimage security?

I was not able to find an explicit statement about the first and second preimage security of SipHash-2-4 or SipHash-4-8 anywhere. I think it should be 64 bit, but I'd feel safer if somebody who has ...
0
votes
1answer
41 views

Is it a bad idea to use PGP encryption for structured/predictable data?

I'm working on an app and need to encrypt some structured data. The data will be turned into a string form (JSON) before getting encrypted. The data format I'm using will always start with a ...
0
votes
1answer
106 views

Are there any quantum-resistant symmetric encryption schemes?

It seems that quite a few currently available encryption schemes will possibly be broken by quantum computing. Are there any symmetric encryption schemes that will remain unbroken (either because of ...
0
votes
0answers
18 views

Does Windows CNG store private information using LSA secrets?

I read that LSA Secrets have the capability of storing data privately, more importantly, ensuring that users without proper permissions cannot access that same data. Windows CNG has security measure ...
2
votes
2answers
80 views

PGP digital signature vs SHA256 HMAC Comparison

First let me admit that I am not a mathematician or a cryptographer. I am responsible for assisting in making a recommendation on a project that is consolidating payment processes within a company's ...
0
votes
1answer
25 views

How to select a 'tweak' used in FE1 mode format preserving encryption?

I'm experimenting with this library Botan which includes a module for format preserving encryption based on FE1 mode. The parameters for the Encrypt method are as follows ...
0
votes
0answers
16 views

What is sLHAE (stateful length-hiding authenticated encryption)?

Can somebody please explaint me how does sLHAE works in TLS? I met this term in some TLS papers and struggled to understand how it works, specifically the "length-hiding" part.As to my understanding ...
1
vote
1answer
49 views

Can Winternitz be easily converted to a many-time encryption scheme?

The Winternitz scheme is typically cited as being an OTS scheme. Can it also be used as a one-time encryption scheme? If it can be used as a one-time encryption scheme, then is it possible to easily ...
1
vote
3answers
309 views

Block cipher does not provide security by itself

What is this statement all about? When I look at a block cipher it seems pretty hard to break it and the mathematics behind insure a good complexity. It may refer to key generation, initialization ...
2
votes
2answers
69 views

Is it safe to use a secret salted hash of a public id for client to prove ownership of id to a server that knows salt but does not store ids?

I am writing a peering server - the server assigns randomly generated public IDs to users, and I want users to be able to reclaim their ids in the future, but only to be able to claim ids that they ...
2
votes
4answers
64 views

Definition of the term “key”

I've looked in many places (NIST, text books, online resources) and I cannot find an answer to the definition of the term "key" from a semantic point of view. Is it the "key" to cipher-texts (i.e. ...
0
votes
0answers
23 views

Does Paillier Cryptosystem work in different message space? [duplicate]

I have a question about Paillier Cryptosystem. Assuming we have $c = Enc(m) = g^m \cdot r^N \mod N^2$ as the output of encryption algorithm, where $N=p_1p_2$ and $m \in \mathbb{Z}_q \subset ...
0
votes
0answers
31 views

If a DES key correctly decrypts one message, what's the probability it's the real key?

Suppose an adversary gets a message-ciphertext pair $(M,C)$, where $C=DES_K(M)$. They do an exhaustive key reach to locate the lexicographically first key $T$ for which $C=DES_T(M)$. What's the ...
7
votes
4answers
260 views

Alice and Bob's crush

Suppose Alice and Bob both want to determine whether the other has a crush on him/her, but they only wish to share the information if the crush is mutual. Is there a cryptographic protocol that makes ...
1
vote
1answer
42 views

Reducing the keyspace for a brute force attack on a chained 64-bit xor

I have a block of data which I know is encrypted using a chained 64-bit xor (sorry if that makes no sense, I'm not familiar with crypto lingo). I know a little bit about what the plaintext should look ...
4
votes
2answers
71 views

Discrete logarithm over prime modulo: small input, large exponent, larger prime

I am considering using modular exponentiation as a one-way hash function. More specifically, here is the scenario. 1) Input ($m$): the input messages are small (16-bit) 2) Exponent ($e$): the ...
0
votes
0answers
28 views

What crypto scheme should I use on embedded m2m system with assymetric uplink/downlink bandwidth?

I am working on implementing info security into custom m2m radiolink communication system, which has some restrictions: MCU based endpoint can transmit to gateway with packets max 16 bytes long, and ...
0
votes
2answers
83 views

Why are there no OTP ciphers?

We all know the OTP is unbreakable and we all love the OTP (judging by the amount of question on this site). The strength of the OTP is not that it is unable to find a word without the key but you ...
0
votes
1answer
36 views

Decrypting DES - limited information

I have a list of DES encrypted strings/data, they come in two lengths, 32 chars hex (16 bytes) or - I believe - 64 chars. I know the key, which is 8 ascii chars (I might add that I am the rightful ...
0
votes
3answers
21 views

FIPS 113 Computer Data Authentication

on the NIST website for Message authentication There is a mention of 2 approved algorithms, i am curious about the first one. the link to FIPS 113, Computer Data Authentication appears to be dead ...
2
votes
1answer
131 views

Are well designed crypographic codes unbreakable? (NOT ciphers)

Codes are not to be confused with ciphers. It is known that all known ciphers are theoretically breakable except the one-time pad and this isn't what the question is about. Some cryptographic codes ...
1
vote
2answers
439 views

What are words in a HASH algorithms

From wikipedia: "They differ in the word size; SHA-256 uses 32-bit words where SHA-512 uses 64-bit words." In this context what do they mean with words? is it the same as a 32 bit (or 64 bit) block ...
0
votes
2answers
71 views

Can I use the output from a DRBG directly as K for AES, or do I need to use a key generator algorithm?

NIST has 3 validated "Recommendation for Random Number Generation Using Deterministic Random Bit Generators" (DRBG's) that are based on NIST SP 800-90A: Hash_DRBG (based on hash functions) ...
1
vote
2answers
92 views

Why aren't zero-knowledge proofs used for authentication in practice?

I read on Wikipedia that zero-knowledge proofs are not used for authentication in practice. Instead (I think) the server is entrusted with seeing a password in plaintext form, which it should then add ...
0
votes
0answers
34 views

Registration and log in through public key cryptography?

I read about zero knowledge proofs. Let's say you want to create an account at a website. You choose a password $p$ and from $p$ you derive deterministically a public & private key pair $(e,d)$ ...
2
votes
1answer
61 views

Yubico's take on U2F key wrapping

I've been reading up on Yubico's implementation of U2F. What I understand so far is that two things are calculated. So upon registration first you calculate a private key by $PrivateKey = ...
1
vote
0answers
45 views

Why does the ElGamal signature have the specific form that it does?

In the original paper, ElGamal(1985) starts his discussion of signatures by saying: "The signature ..... is chosen such that the equation: $\alpha^m = y^r r^s \text{mod p}$ (equation 3 from the ...
0
votes
2answers
92 views

SHA-512 partial preimage

I was looking at how SHA-512 works, and I have a question. Imagine I want an input $N$ of 512 bits whose hash in hexadecimal starts with the digits 12345678. How ...
1
vote
2answers
92 views

Integer encryption preserving equality

I have read too many different options for encryption that I now feel quite lost. I need a simple, secure (don't we all) scheme for encrypting integers (32-bit) with the following requirements: ...
0
votes
1answer
46 views

Zero knowledge / proof of knowledge sudoku solution

I recently started a coursera course "cryptography 1" provided by Stanford university. In one point when explaining zero proof knowledge the instructor mentions the following: Almost any puzzle ...

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