3
votes
2answers
105 views

Is it safe to initialize secret keys by just reading /dev/random on Linux?

For a software, I don't want the user to choose weak keys, so I plan to just read the needed number of bytes from /dev/random to create the needed secret keys. Is it safe to do so?
31
votes
3answers
413 views

How does RSA compute such enormous numbers?

So I have been reading and learning a lot about cryptography lately and in particular asymmetric ciphers such as RSA. One thing that I am curious about but never seems to be mentioned is how the ...
2
votes
1answer
160 views

RSA 1024 bit forge a new matching signature from a chosen message

I have an RSA signature scheme with 1024-bit key where I know the following: Public modulus $N$ Public exponent $e=3$ A lot of signatures Summary: To compute a signature, an MD5 hash is ...
3
votes
2answers
627 views

Is it possible to apply hill-climbing algorithm to Diffie–Hellman?

If Eve intercepts all the values communicated between Alice and Bob in a Diffie–Hellman key exchange, and applies the hill-climbing algorithm to reverse the modulo function, how will the algorithm ...
1
vote
0answers
25 views

Data in frequency modulated audio [closed]

I'd like to have a peek at the firmware of a piece of Hardware. Its firmware is available as a .wav file to be uploaded via audio jack. https://drive.google.com/open?id=0B6S_PcWWM1YlQnNwT2FSMnFzVE0 ...
1
vote
0answers
28 views

Is a timing side channel attack effective when the leaked information is related to the result of a hash?

I'm writing a function to act as a cryptographic hash of a number within a range that returns another number of the same range. The catch is that the result needs to have certain properties. I run a ...
0
votes
1answer
50 views

How can I prove I have a certain Facebook account by signature?

I would like to know how to prove I have certain Facebook account (or that I can login to that account).
2
votes
0answers
20 views

Does the length of the keyword used for keytable for Playfair matter?

So for Playfair, we choose a keyword and put that in the keytable with no duplicates. Then, we fill the rest of the table with alphabets in order that are not in the keyword without 'J'. Does the ...
1
vote
1answer
47 views

Is it safe to use MD5 in a proof of work system?

Here is the POW system: you are given a string and you need to compute a suffix so that first few bits of the MD5 value are all 0. I know MD5 is collision vulnerable, but is it safe to use MD5 here, ...
1
vote
0answers
27 views

ephemeral-ephemeral ECDH and MITM attack [duplicate]

ephemeral-ephemeral ECDH is it susceptible to MITM attack ? if yes, can you please give me a detailed answer ( Workflow that can be followed by the attacker) and how we can prevent this attack ...
1
vote
1answer
50 views

Byte size of Diffie-Hellman public values

I have a scenario that uses RFC-3526's Diffie-Hellman Group 14 for 2048 bit key exchanges. From the document, it specifies the P (prime) value in hexadecimal value as: ...
0
votes
3answers
72 views

Perfect hash function

Is a perfect hash function always bijective ? In Wiki "In mathematical terms, it is a total injective function" but it does not mean, that it is bijective.
0
votes
2answers
69 views

hash functions preimage and second collision resistance [duplicate]

A hash function H is secure in terms of pre-image resis-tance. Does this imply that H has second pre-image (aka weak collision) resistance?
1
vote
0answers
64 views

Perfect Secrecy of AES file Encryption

Why does AES file encryption not ensure perfect secrecy? I understand that $\Pr[E(K,M_1)=C_1] = \Pr[E(K,M_2)=C_2]$ given $M1\neq M2$ holds for perfect secrecy of a scheme. However, this seems to hold ...
2
votes
0answers
69 views

Problem with applying threshold scheme

For a report on threshold signature schemes, I have to explain a threshold signature scheme and give a simple example with numbers. A threshold signature scheme is a scheme in which a network of n ...
1
vote
1answer
87 views

Bcrypt input length vs collisions

I am currently implementing oauth2 bearer token authentication and am storing the tokens bcrypt encrypted. My question is how long should the tokens be to achieve maximum security. E.g. at what length ...
5
votes
2answers
181 views

lcm versus phi in RSA

In textbook RSA, the Euler $\varphi$ function $$\varphi(pq) := (p-1)(q-1)$$ is used to define the private exponent $d$. On the other hand, real-world cryptographic specifications require the ...
8
votes
3answers
487 views

Why do we require a CSPRNG's output to be indistinguishable from true random?

Everywhere I read, indistinguishability of output from true random is stated as a requirement for CSPRNGs. However nobody bothered to give the rationale for such a strong requirement. Specifically, ...
1
vote
1answer
75 views

How is RSA able to prevent brute forcing using the public key?

Bob calculates a private and public key. Bob sends his public key to John. Jeff is a third party unwanted member and manages to snatch the public key mid-transfer. John encrypts his message ...
2
votes
2answers
40 views

Is it secure to use TOTP with same key and different time-counters?

If I use TOTP to generate codes with different "expiration" time, using the same key for HMAC, will I create some kind of weakness?
1
vote
1answer
86 views

How can IND-CPA encryption be identity revealing?

This is problem 10 of Chapter 4 "Symmetric Encryption" (pdf) from Lecture notes by Bellare and Rogaway: An IND-CPA secure encryption scheme might not conceal identities, in the following sense: ...
0
votes
2answers
39 views

Certificate Path Verification of X509 Certificate

I have the trusted root certificate which I am validating using the self signed key. I also have the intermediate certificate, which i am validating using the root certificate. Now when i am ...
4
votes
1answer
64 views

How to exctract ECDH parameters from an OpenSSL-generated $G$?

I'm using ECDH for generating ECDH public parameters (p,a,b,G,n), I try to get this values using openssl ecparam -in cert.pem -text -noout For ...
2
votes
1answer
92 views

Stream Ciphers and cycling questions

For all PRNGs (including CSPRNGs) lets say there is a sequence x, y, z, then when the PRNG cycles back to x, then the sequence following it will be exactly the same as before. Is this true for all ...
8
votes
4answers
479 views

Can an encryption method be used as a hash function?

As I understand, there are a few requirements for a good hash function. Hard to find any message from a given hash Hard to find any 2 messages which give the same hash A single bit change in the ...
2
votes
1answer
94 views

What is the difference between CPA and IND-CPA?

I am writing a paper and I got comments from the reviewer that I don’t really understand. Is there any difference between a CPA (Chosen Plaintext Attack) and IND-CPA (Indistinguishability under ...
8
votes
1answer
275 views

Quantum on hash

Perhaps this has been answered before. Grover's algorithm should result in a 256 bit hash being complexity 128 bits to crack. I was wondering, what if you had a 512 bit hash , and xor'd the lower 256 ...
1
vote
0answers
29 views

Why the group order has to be prime for pairing-based cryptography [duplicate]

I'm trying to get into pairing-based cryptography and I don't see why the group order of the group G in the pairing function e:G*G-> G_t has to be a prime number. I don't find an argument why ...
1
vote
1answer
128 views

Is it possible to create “non overlapping” RNGs?

For example, let's say I want two cryptographically strong RNGs (R1 and R2). And I want them to have the following property: R1 (resp. R2) will never generate the same random number twice. R1 (resp. ...
1
vote
1answer
44 views

Is this distributed OTP scheme secure?

This is for a distributed system: we don't want to have to maintain synchronization of random streams neither enforce uniqueness of pads because this would require some synchronization. Alice and Bob ...
2
votes
1answer
53 views

Has there been any research on entropy efficient information-theoretically secure PRNGs?

I have an idea for an research project, but I am first wondering if it has been researched or implemented before. I think I have a way to come up with a set of PRNG algorithms which have the ...
3
votes
0answers
49 views

Combining md5 collisions to create more collisions

Given X1 and X2 such that md5(X1) = md5(X2) and Y1 and Y2 such that md5(Y1) = md5(Y2), and knowing the following property of md5: if md5(a) = md5(b), md5(a|s) = md5(b|s) is there a way to find ...
1
vote
1answer
77 views

DES and using the S-Box 1

Can someone please check my work and correct me if I am wrong, I am just starting to learn about DES. I am trying to solve the following problem: Show that ...
1
vote
0answers
63 views

Encrypting a 160-bit plaintext into a 160 bit ciphertext with a 128-bit Block Cipher [closed]

So I have a kind of interesting issue. I have a field in my data store which must take exactly 160 bits of information. Some users will choose to make this data encrypted, some won't, so some of those ...
0
votes
1answer
69 views

how to get the file used to brute force any encryption method [closed]

Bitlocker as example uses AES 128 Bit encryption as default - if it was brute forced how it can be done , I mean where's the file that will be brute forced to generate the password (If I'm right that ...
1
vote
0answers
32 views

PKCS#11 Sessions

I am maintaining an application that uses PKCS#11 to talk to a smartcard. Somehow a session gets generated, but i cant figure out where in the code. I am using c# and the PKCS11Interop wrapper. The ...
2
votes
1answer
59 views

Is it possible to add error propagation to OTP?

What would be the recipe to add error propagation to a one time pad? I.e. if I change a single letter in the clear text message, I want the encrypted message to change starting from that letter and up ...
6
votes
1answer
187 views

Why does GnuPG save an array of remainders when generating prime numbers?

In looking at GPG's gen_prime() function, found within the cyphers/primegen.c file of ...
-1
votes
0answers
22 views

What is the process to get the n future key for DUKPT? [closed]

I need to get the n future key from my BDK and KSN.
2
votes
2answers
60 views

Diffie-Hellman secret key choices

I'm trying to understand why the secret keys used by Alice and Bob in Diffie-Hellman are $a,b ∈ ℤ∗p$. Say $a$ is $p - 1$, wouldn't the transmitted $g^a$ be 1 mod $p$ by $FLT$? Now anytime a ...
1
vote
2answers
60 views

How to generate backup key for PBKD functions?

I would like to encrypt some files using AES, Ill derive key from password using some standard PBKD function and use that as AES encryption key. My question is, if user forgets the main password, ...
3
votes
1answer
61 views

Why is GCM only usable for ciphers with a 128-bit block size?

All block cipher modes of operation that I understand are generic schemes. They are not restricted by key size or block size. So why is GCM restricted to 128-bit block size?
1
vote
1answer
91 views

How to use AES correctly in BPS Format Preserving Encryption

I have several questions on using AES 128bit in the BPS format preserving encryption Which modes are acceptable? (Should the block cipher used at each round be deterministic (ECB) or probabilistic ...
1
vote
1answer
68 views

Which ECB ciphertext stealing scheme is this?

I am stuck with identifying ciphertext stealing method with the following properties: mode of operation is ECB; recommended padding scheme for this application is PKCS#7, but apparently it is not ...
1
vote
0answers
65 views

Powerline password conversion [closed]

I read this post from Ben Tasker describing how to take control of a powerline network. Since I am interested in security, I tried to do the same thing, to see if it was possible. I used Devolo ...
3
votes
1answer
120 views

How can cryptographic signatures be somehow linked to a physical signature?

A few days ago, I was asked to sign an online document over DocuSign as well as on SignEasy, any the signature were accepted just by a physical signature sent over email or on the app. They did not ...
1
vote
0answers
33 views

Is it possbile to get same set of public and private keys twice while creating CSR ? If so where does the conflict happens !?

I'm new to cryptography and please clarify if my below assumption is wrong. Lets assume, that two different banks creating CSR and they get identical public and private key pairs of RSA. In such ...
2
votes
2answers
67 views

Is it safe to use single-block AES for mutual authentication?

I read the question Symmetric mutual authentication with client using a derived secret and its answer which, if I'm not mistaken, assert that it should be safe to use the proposed protocol for mutual ...
1
vote
1answer
47 views

How exactly is an enigma simulation software supposed to encrypt alphabets?

EDIT: The model I'm trying to make is "Enigma 1". I learned initially about it from a book called "Code Book" and then looked at it in detail from its wikipedia page. The rotor wiring and other ...
2
votes
1answer
75 views

Why is the tweak length 64bit in BPS FPE algorithm?

In the algorithm for BPS Format Preserving Encryption Is this tweak always the same length (64bit)? Why did they choose the length 64bit for the tweak?

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