All Questions

1answer
36 views

Differences between Work Factor and Time Complexity

I am interested to know if work factor means the same thing as time complexity. Quoting Work Factor : Uncovering keys in cryptosystems The Work Factor of a cryptosystem is related to its ...
2answers
56 views

Are there any known weaknesses with ElGamal algorithm?

I am working on a messaging system and plan to use ElGamal asymmetric encryption to protect the message contents during storage and transmission. (This would be in addition to TLS used during ...
0answers
69 views

Zero Knowledge Non Interactive Proof with random oracle

I am trying to write an assay about Non Interactive Zero-Knowledge proofs and would like to take the simple discrete logarithm problem example fallowing the Feige-Fiat-Shamir heuristics. I understand ...
2answers
130 views

PGP String to Key specifiers

I've been reading through the PGP Standard and here I'm a little confused. This section is discussing converting string data to a session key. I'm confused about the paragraph in bold. First off, what ...
1answer
29 views

Would the Fiat Shamir identification scheme be more secure if I design it with an exponents higher than 2?

Let's say both Prover and Verifier would use nth power instead of 2nd when creating public keys and when verifying. I know it would slow it down but would that cause the protocol to be more secure?
7answers
2k views

How exactly is “true randomness” defined in the realms of cryptography?

Especially in relation to stream ciphers, I frequently read about (sometimes theoretical, sometimes practical) attacks that are able to "distinguish a ciphertext from a truly random stream". What's ...
3answers
2k views

The exact difference between a permutation and a substitution

I've noticed confusing definitions about permutation and substitution, preventing to make the difference. A permutation changes the order of distincts elements of a set, but this can be writen as a ...
1answer
64 views

What would a backdoor in symmetric key cipher look like? [duplicate]

Pretty much what the title says. DES was suspected of having one, but I couldn't imagine what it could possibly look like if only the NSA knew how to use it. Dual_EC_DRBG's backdoor is asymmetric, but ...
0answers
64 views

Working a problem that uses RSA encryption:

To overcome weaknesses of the textbook version of RSA encryption, commonly some form of padding is applied.Consider the following suggestion for an asymmetric RSA-based encryption scheme: Key ...
1answer
49 views

Why is C_digest defined in PKCS#11?

Digesting doesn't require any key and can be performed on the client side. Why does the PKCS#11 token interface standard have a C_digest method? For example, why should I send my data to a PKCS11 HSM ...
1answer
114 views

Multiple private keys for single public key

I am currently working in security in mobile ad-hoc networks. I have several clusters, and I want to send some data encrypted with its public key, from the cluster head to the cluster members. I ...
2answers
559 views

If we can find prime numbers larger than 17 milion digits, why can't we find all 1024bit primes? [duplicate]

"Largest Known Prime Number Discovered; Has 17,425,170 Digits" http://www.sciencedaily.com/releases/2013/02/130213225424.htm If we can find prime numbers larger than 17 milion digits, why can't we ...
3answers
276 views

decrypt numbers multiplied by a certain floating point number

A friend has about 10K numbers in a an excel sheet. He wanted to encrypt these numbers in order to share the file with a 3rd party that will help him reorganize the tables. What he did, to hide the ...
0answers
15 views

Runtime of a particular step of karatsuba algorithm [on hold]

I am new to algorithms and was trying to calculate the runtime cost of each step of the karatsuba algorithm. Assuming you know what the karatsuba algorithm is, So I was not sure of the calculation ...
1answer
30 views

Standard serialization format for libsodium-based messages

Does anyone know of a standardized serialization format which can be (or already is) widely used for encrypted messages? For a variety of reasons (mostly complexity, age and poor support across a lot ...
1answer
34 views

GCM implementation

I want to write GCM implementation myself (only for research purposes). So far, I have successfully written CTR implementation (for AES), but now I ran into few problems with GCM. If I'm not wrong, ...
2answers
170 views

How to choose an algorithm

I have some understanding of Cryptography and I would like to know if there is a tool or website to help me choose an algorithm based on my own needs (I'm being vague in purpose). I'm looking for a ...
1answer
24 views

Is this JS library using openssl genrsa -rand improperly?

pem, a JS wrapper around openssl, has the following code in it: var params = ['genrsa', '-rand', '/var/log/mail:/var/log/messages', keyBitsize ]; Am ...
6answers
8k views

Difference between encrypting something and hashing something

What is the difference between encrypting something and hashing something? in what situations would I want one or the other?
0answers
67 views

Exponentiation with fully homomorphic encryption [duplicate]

I have often heard that because a fully homomorphic encryption scheme allows for both additions and multiplications on encrypted data, most other operations can be simulated. I don't understand how ...
1answer
45 views

Explanation of multivariate cryptography [on hold]

How do the key generation, encryption, decryption, signing, and verification processes in multivariate cryptography work? How about an example or at least a simplified general one? Also, what is the ...
2answers
65 views

Why can the last block contain a full block of padding in CBC Encryption?

I'm trying to understand the SSL Poodle Attack and I'm wondering why the last block of a CBC Record can be full of padding? Wouldn't that mean that the useful data was already a multiple of the key ...
1answer
58 views

Hashes and Ciphers [on hold]

So I'm brand new to cryptography, I'm confused on a few fundamental issues, and my normal avenues of research aren't bearing any fruit. I'm hoping someone can describe the relationship between ...
0answers
15 views

PHP: How to show supported client ciphers [on hold]

How to print a list of ciphers offered in ClientHello? How does e.g. mikestoolbox.org or hotaru.thinkindifferent.net show which cipher is used / offered by client? Thanks for helping.
3answers
268 views

How does an oblivious test of plaintext equality work?

Assume an ElGamal Cryptosystem. Assume a set of three players, $P_1$, $P_2$ and $P_3$. The private key $x$ is shared among the players. The player $P_1$ has a piece of the private key $x_1$, $P_2$ has ...
0answers
38 views

Are there any asymmetric composite order group bilinear pairings?

Are there any asymmetric composite order group bilinear pairings? Is there a drawback of asymmetric over symmetric bilinear pairings of composite order either in efficiency or in security ?
1answer
48 views

Send an encrypted question and return answer without decryption

Oke bear with me for a minute. Once upon a time someone mentioned a hypothetical way where you would send an encrypted question to Google and Google would return an answer without decrypting it. As ...
0answers
8 views

Acceptably secure solution for users to log in with a short unique code only (no username) [migrated]

I am creating a website whereby users are given an account by invitation only, and are sent a unique code by post. Users can then log in (at least the first time) by entering the code only. The goal ...
1answer
316 views

Cryptool - DES (ECB and CBC ) - double encyption

So, I uploaded a text file in Cryptool and encrypted it with DES-ECB with the key FF FF FF FF FF FF FF FF. I encrypted the cipher text again, with DES-CBC using ...
1answer
27 views

PBKDF2 for login key, scrypt for encryption key

I need to derive two keys from a single password client side. One for in-browser login, the other for encryption. Is the following secure ? ...
3answers
45 views

Reduction of a modular exponentiation's base does not change the result

Can anyone help me to prove this property used in the RSA correctness theorem? $a^b\bmod{n}\equiv (a\bmod{n})^b\bmod{n}$ Specifically, here is what I have done: this is what i mean. i can't ...
1answer
2k views

How to communicate by email with forward secrecy and deniability?

My correspondents and I would like to communicate privately by email. We used to employ PGP but that might have been shooting ourselves in the foot. PGP doesn't have forward secrecy. If any of our ...
0answers
40 views

websites to have people break encryptions [closed]

I have built an encrypted text editor and was wondering if there were sites out there that you could post encrypted text and have some actual smart people try and break it. I would like to test this ...
2answers
60 views

Solve the congruence using Pohlig-Hellman algorithm

Use the Pohlig-Hellman algorithm to compute a solution to: $3^x\equiv 2 \pmod {65537}$ My attempt: $p-1 = 65537-1 = 65536= 2^{16}$ $x= 2^0x_0+2^1x_1+2^2x_2+...+2^{15}x_{15}$ For $x_0$: ...
0answers
86 views

I am working on a cryptographic scheme and I need to rely on the following problem, which I have nicknamed the "Hybrid Decisional Bilinear Diffie Hellman (hDBDH)" problem: Let $e: \mathbb G_1 ... 1answer 87 views Hardness of problem related to bilinear pairings Let$e: \mathbb G_1 \times \mathbb G_1 \rightarrow \mathbb G_T$be an efficient bilinear pairing. Note that the pairing is symmetric (i.e., Type 1). The problem is, given$g \in \mathbb G_1$and ... 1answer 106 views Gap problem for Learning With Errors Informally, a "Gap problem" arises when solving the computational (or search) version using an oracle for the decisional version. This definition of Gap Problem was introduced by Okamoto and ... 1answer 446 views understanding forking lemma Every time when I read a paper that has digital signature, when it comes to prove the security of a digital signature scheme, many chances that the author will use the forking lemma. The forking ... 1answer 651 views Why are the outputs of the md5sum tool and Crypto++'s MD5 different? Could you please tell me what is the difference of coreutils' md5sum and sha*sum tools (... 2answers 136 views AES ECB experiment Generally speaking, ECB mode shouldn't be used. ECB seems to be more of a basic building block than anything else. Because I thought it would be interesting to experiment with encryption (this method ... 0answers 36 views Using the chinese remainder theorem as a part of the proof, show that 2^700 = 1 mod 3625 [closed] Using the chinese remainder theorem as a part of the proof, show that 2^700 = 1 mod 3625 Using the chinese remainder theorem as a part of the proof, show that 2^700 = 1 mod 3625 4answers 13k views Can you help me understand what a cryptographic “salt” is? I'm a beginner to cryptography and looking to understand in very simple terms what a cryptographic "salt" is, when I might need to use it, and why I should or should not use it. Can anyone offer me a ... 1answer 157 views How does hash function in Elgamal signature scheme prevent existential forgery attack? I have heard that hashing the message M prevents an existential forgery attack. I was wondering how. 0answers 38 views What aspect of elliptic curve encryption paradigms makes them especially susceptible to quantum based attack algorithms? This was a statement made during a talk at today's DFN-CERT conference but unfortunately it wasn't explained further. Can anyone shed light on why elliptic curves are susceptible to quantum based ... 2answers 103 views Randomness re-use in LWE encryption scheme Let me describe the scheme first, it is the scheme proposed by O. Regev when he introduced the LWE assumption.$sk = \textbf{s} \in \mathbf{Z}_q^npk = \textbf{A}\textbf{s}+\textbf{e}$where ... 0answers 11 views Getting Certificate KeyContainerName to initialize CspParameters [migrated] How can I get the name of a Key Container that's in a smart card required for initialization of CspParameters? CspParameters^ cspa = gcnew CspParameters(ProviderType, ProviderName, keyContainerName, ... 2answers 51 views Schnorr's identication protocol Schnorr's identification protocol is said to be a honest verifier zero knowledge protocol. Does it imply it will not work if the verifier is dishonest? I'm wondering if this is the case, it would ... 2answers 68 views AES GCM vs other encryption modes in embedded environment for network traffic I'm doing a lot of research since I'm doing an internship for a company where I need to upgrade their security level. Their own protocol needs a cryptographic upgrade and I'm leaning towards AES since ... 2answers 56 views ECDSA Public key randomness If I have a 256bit ECDSA public key how likely is it that the same public key will be generated by another person. Will it take on average 2^256 tries to generate same public key? If I xor the first ... 1answer 53 views RSA Key composition I'm trying to figure out how it is composed the RSA key. Follow what I know : For a RSA 2048, 2048 is the bit length of the module. The public key is composed by$(e,M)$when$e\$ is the public ...

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