1
vote
1answer
25 views

Comparing Difference Distribution Tables

I have been studying the Diff. Cryptanalysis and finding it hard to do a problem. The problem is I have calculated the tables programmatically and found that the second table has a max value of 6 ...
1
vote
1answer
28 views

PBKDF2-SHA256+SHA256 for password storage

I recently came across an interesting paper detailing the use of hardened session cookies. Each cookie includes a preimage of the password hash, and the preimage is hashed once more and compared to ...
2
votes
1answer
35 views

Are variable-length crypto hash functions still susceptible to collisions?

I just recently learned that the SHA-3 finalist Keccak allows for variable length output. As the only answer to this question states, "[it] need to have an output length at least equal to the input ...
1
vote
0answers
37 views

PBKDF2 Salt and Password Ordering

I am currently reading about PBKDF2, and understand that the salt is used only once, while the password is used multiple times in the computation of the final key (see this question). How would the ...
1
vote
0answers
32 views

How to distribute symmetric key between $n$ entities?

If there are $n$ servers for broadcasting a symmetric key in such a manner that following holds: No server alone can find the key $K$ alone. Any two servers can pass $k_i$ and $k_j$ such that ...
2
votes
1answer
42 views

Beta spec: “intermediate hash-code”

I've read the following two sentences within a beta protocol specification, which references ISO/IEC 7816-8 for PSO:HASH which already contains notions of a "partial hash". The off-card entity is ...
1
vote
0answers
22 views

Type G Bilinear Pairings

I was reading PBC and its implementations for finding pairing parameters. I am particularly interested in implementing a BLS signature scheme with 20-byte (160-bit) signatures ("short signatures"). ...
-1
votes
0answers
29 views

What c++ crypto library might I use for XTS mode? [on hold]

Ideally, I would like to use crypto++ for it's simplistic and straightforward API. This has so far worked very well in a domain where data needs to be read from / written to at random seek locations: ...
0
votes
0answers
31 views

what is the motivation and need for lattice-based systems in epassports in post- quantum computers era?

AS shor's algo would break the RSA and DH (though I dont understand the complete steps of shor's algo), all protocols of epassports would be broken so why cant it be not broken with lattice-crypto, ...
1
vote
1answer
38 views

EAX: OMAC and CMAC

OMAC is specified as the underlying algorithm to provide authentication within the EAX authenticated encryption (with associated data). Would that be OMAC1 or OMAC2? If it is OMAC1, does that mean it ...
0
votes
0answers
44 views

Proof for composed signatures

Assumes that we have 3 signature algorithms, $S^A$ with key pair $(sk^A,pk^A)$, $S^B$ with key pair $(sk^B,pk^B)$,$S^C$ with key pair $(sk^C,pk^C)$. We denote by $\epsilon$, $\epsilon'$ and ...
3
votes
0answers
32 views

OCB and GCM security

Is OCB as secure as GCM or CCM ? Since OCB design is quite different from GCM and CCM, I was wondering if the security properties of these latters are satisfied by OCB, as well. Thank you.
-2
votes
0answers
46 views

Why is composite order bilinear group used for scenarios needing highly secure systems?

Why composite order bilinear group is used for scenarios that need highly secure system compare to prime order bilinear group that used for efficiency? We know that composite order bilinear group are ...
3
votes
1answer
75 views

Proving Non-Existence of ECC Backdoors

In light of the NIST Dual EC DRBG scandal, I was intrigued by a NIST slide (slide 9) that said the two points P and Q can be chosen so that the chooser can prove they don't have a backdoor. This ...
-5
votes
4answers
215 views

Found a way to crack AES-128, what now?

I have just found a way to crack AES-128 in a reasonable time (1-2 days). How do I publish and prove this? I remember reading about lots of people who cracked DES and other ciphers but how did they ...
3
votes
2answers
158 views

Attacking unuauthenticated RSA

In symmetric cryptography, a scheme is not considered secure if the data transmitted is only encrypted. The adversary will be able to modify messages to generate encrypted messages of his choice ...
-1
votes
6answers
116 views

Ideas for a Crypto competition for teenagers

I have to hold a workshop for teenagers at our university about Cryptography. They will be about 16 years old. I'm planning to do a competition with prizes - there will be different tasks and each one ...
-4
votes
3answers
54 views

Solution with high decryption cost and low encryption cost

I am looking for any cryptographic solution that will meet those requirements : Only known method to get the encrypted string need to be brute force. Decrypting on modern computer not more than ...
1
vote
1answer
47 views

Counter Mode: how to choose the nonce part of the counter? [duplicate]

Suppose: The "counter field" is about: NONCE || CTR-VALUE. I have multiples messages $M_a, M_b, M_c, \dots$ Each message can be divided into x-bits blocks ($M_{a1}, M_{a2}, M_{a3}, \dots$). Each ...
3
votes
1answer
212 views

Can all asymmetric key pairs be reversed?

After reading about public/private key cryptography, there are still a few points I don't really understand. Based on the way (I understand) challenges work, the public key is used to encrypt a ...
1
vote
0answers
43 views

Groth-Sahai proofs and hardness assumptions

I am learning Groth-Sahai NIZK proof system for Bilinear groups. While going through the literature, I am getting confused on how the proof system is related to Subspace Decision, SXDH or DLIN ...
2
votes
1answer
72 views

One Way function and Merkle Damgård

Is it possible keep the "one wayness property" of certain one way function in Merkle-Damgård construction? I'm asking this question because according to Collision-Resistant hashing: Towards making ...
0
votes
0answers
62 views

RSA and ECDSA Certificate Sizes

Is there a table (or a whitepaper from official sources) that compares the size of X509 certificates generated with RSA (starting from 1024 bits) and ECDSA (starting from 160 bits) ? Thanks for the ...
-1
votes
1answer
79 views

What's the best packet cipher mode for use with UDP for example? Advantages or disadvantages of any alternatives?

Cipher modes typically assume data is streamed or read from a reliable channel with guaranteed ordering. However, many communication transports, such as UDP, are not reliable and don't guarantee order ...
1
vote
2answers
98 views

Efficiently map $2^n$ unique 64-bit vectors to $2^n$ $n$-bit vectors where $n < 64$? [on hold]

Is there an efficient way to map $2^n$ unique 64-bit vectors to $2^n$ $n$-bit vectors where $n < 64$?
4
votes
1answer
90 views

What's the consequence of having a short IV? Is one mode better in that case?

I've read lots about null-length IVs being bad for most modes. In a scenario where passing a 128-bit IV along with each message isn't feasible, how would generating the IV from a smaller passed-along ...
8
votes
1answer
119 views

Proof of Communication

I desire an algorithm in which Alice sends a block of data $X$ to Bob, with proof that the data was both sent and received. Ideally this would take the form of a public-key signature of the block $X$ ...
7
votes
2answers
331 views

Is it secure to derive an AES key from a MAC?

I'm working on a project where we need to encrypt a large number of files and store them on the cloud. And I'm wondering if the following process would be secure (we have a “Hardware Security Module” ...
-2
votes
1answer
80 views

Which causes longer “break” time (in general)?

In general (if possible to determine) which would make an output harder to turn into plain text with a computer? Extreme Length (minor complexity change) Extreme algorithmic complexity (minor length ...
3
votes
1answer
48 views

Convergent Encryption: integrity and authenticity

I have one question about convergent encryption. Suppose I use AES-256 in CBC mode. I need a 256 bits key and a 128 bits IV. If I use SHA-256 to hash one file, then I can use directly that hash as ...
2
votes
2answers
50 views

Maximum password length in PBKDF2

Haven't found any clear cut answer in Google so its up to you guys: DK = PBKDF2(PRF, Password, Salt, c, dkLen) Here, what is the upper limit of password length? ...
3
votes
2answers
50 views

CBC-MAC key can be added to ciphertext?

I use AES both CBC and CBC-MAC to encrypt some stuff. I generate one key for CBC and one different key for CBC-MAC. Does the second key (for CBC-MAC) need to be secret? How to join such key with the ...
1
vote
0answers
61 views

ECC cryptography with shorter signature when not needing high security?

I am new here and fairly new to cryptography, so if I say something wrong, let me know. I am trying to set up a system where a user can receive a temporary license key over the phone, put it into ...
2
votes
1answer
71 views

Variants of AES? [on hold]

Would variants of AES provide the same level of security as AES, say by just replacing the S-box with another one, MDS matrix of Mixcolumn, etc.?
-2
votes
0answers
50 views

mixing SPN and Fiestel

Shall we design a block cipher by mixing a SPN and Fiestel together?Is it possible to combine the logics of AES and DES resulting into a good block cipher
-2
votes
0answers
59 views

How can one design a good block cipher? [on hold]

Are there any other methods for designing a block cipher than Substitution and Permutation Network (SPN) and Feistel Network?
3
votes
2answers
110 views

Is this a plausible PBKDF?

Background: Hello, I'm working on a hobby project in which I might want to implement a key derivation function within a somewhat resource limited embedded system. For standard crypto functions, I ...
-1
votes
0answers
22 views

Digitally sign and verify a file using private/public keys and OpenSSL API [closed]

I am signing a file using a private key and want to verify it using a public key. Until now I am only able to verify it with the privatekey/certificate file. This is how I generate the keys: ...
2
votes
2answers
63 views

Diffie–Hellman Ephemerality Nomenclature

Below is a short excerpt of available DH cipher suites available on a machine. I understand EDH is ephemeral DH, and that ECDH is for Elliptic-Curve DH which is computationally faster. ECDHE is both ...
2
votes
1answer
37 views

ElGamal signature scheme: Why is r included in s

In the ElGamal signature scheme we calculate a signature for a (hashed) message $m$ as $r \equiv_p g^k$, $s \equiv_{p-1} (m - xr) k^{-1}$ and verify it by checking $g^m \equiv_p y^r r^s$. Here ...
0
votes
0answers
21 views

Trying to use XSalsa20 but the decrypted text breaks of halfway [closed]

Hi the following is a small CPP code that I wrote to try out XSalsa20 cipher. ...
1
vote
0answers
51 views

Recover plaintext from truncated ciphertext using AES for FPE

I am trying to implement an FPE for a 19-digit long number. I am trying to follow the lecture of Prof. Dan Boneh and here is how I understand it: Get the nearest power of two greater than $10^{19} ...
1
vote
0answers
39 views

IND-CCA2 secure schemes without Plaintext Awareness?

I have been reading up on IND-CCA2 security and was wondering: Are there efficient IND-CCA2 secure schemes that do not require plaintext awareness? I'm guessing yes - could someone point me to these ...
-1
votes
0answers
62 views

Design of S box [closed]

What is the method to replace AES s box?. Is it possible to generate all the S box ,permutation of 0 to 255 using GF 256 logic similar to AES
2
votes
0answers
40 views

Regular MACs vs Carter-Wegman MAC

Carter-Wegman MAC variants (VMAC, UMAC etc) are known to be very fast and efficient when compared to MAC algorithms that are based on block ciphers and compression functions (like HMAC, CMAC etc). ...
1
vote
1answer
63 views

Private Key - Memory Lifecycle

I often heard about private key storage, but rarely about key life cycle in memory. For example, when SSL is used from one peer, the private key is used to sign messages or decrypt other peers' ...
4
votes
2answers
543 views

A patched SHA1 attempt for password verification

This is a classical scenario: For our web based authentication platform we have a username and a password field. User enters these values and presses Log In. The browser gathers the user data, ...
-1
votes
0answers
58 views

Can anyone help me decrypt this? [closed]

We were told that GREENENVY was a hint but I don't know how to do anything from there. AU/W/ACBXMSN/IEHOFIE/NZ
5
votes
6answers
1k views

Cryptography vs Security

This may sound a little bit of basic but here it goes… Which of the following is correct? “Cryptography is under the security field”, or “Security is under the cryptography field?” Cryptography ...

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