1
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1answer
233 views

Frequency analysis of Vigenere Cipher

For Vigenere cipher, I understand Find period first (say we have p = 6) Find highest frequency of letter in each group (from 1 to 6) and assume it is "e" in plaintext What if we have more than ...
1
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2answers
143 views

Operation which needs much computing power to be created, but just a little to be solved?

Does somebody know a cryptographic/mathematic operation, that needs much computing power to be "encrypted"/"created" but doesn't need much power to be "decrypted"/"solved"?
1
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1answer
175 views

How to encrypt letters less than block n using Hill Cipher

I am learning about Hill Cipher and know that it is a block cipher where each block of n letters (considered as an $n$-component vector) is multiplied by an invertible $n \times n$ matrix, again ...
1
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1answer
98 views

Is it possible to 'fake' time for TOTP? (Time-based One-time Password)

TOTP (Time-based One-Time Password) Algorithm is used in Two factor authentication. I understand the algorithm and that current time is used as a variable to generate a token. Wiki page for reference: ...
1
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1answer
140 views

How can convert affine to Jacobian coordinates?

I have a point in affine coordinates: $(x,y)$. What should I do when I want to convert to $(X,Y,Z)$ in Jacobian coordinates? I need it for calculating ECC in a prime field.
1
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1answer
266 views

How costly is to find millions of large prime numbers for RSA?

Consider I need to assign a large distinct prime number to each element in a large set. This must be deterministic so the function always gives me the same prime to the same value. What is the most ...
1
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1answer
93 views

RFC3447 OBJECT IDENTIFIER semantic

http://tools.ietf.org/html/rfc3447#appendix-B.1 ...
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1answer
65 views

Key escrow on indistinguishability games

Does it mean that when PPT attacker is breaking an indistinguishable based (equivalent with semantic security) game with non negligible probability that he is able to infer the secret keys either on ...
1
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1answer
173 views

Correctness vs Completeness

What is the conceptual difference between the definition of correctness and completeness in verifiable cryptographic protocols? They justify that if a statement is correct then the verification should ...
1
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2answers
230 views

Strength and weaknesses of this JavaScript charCodeAt based login script

I know of a company on their website who are using this very basic password login page written in JavaScript. This doesn't seem very secure at all, because in the html source code it shows where the ...
1
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1answer
124 views

EC Public Key length in ASN.1 DER

I have two X.509 certificates in DER format. A: ...
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2answers
276 views

Random vs. Fixed Paddings

Is there any consensus (i.e. are there any research results) on the benefits and drawbacks of various padding schemes? Generally there seem to be two kinds of them: random paddings, like ISO10126 ...
1
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1answer
196 views

Is Rabin's cryptosystem secure against known-plaintext attacks?

I've bee learning about Rabin's cryptosystem, and I already know that Rabin's cryptosystem is vulnerable to a chosen-ciphertext attack, but I was wondering, is it also vulnerable against ...
1
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1answer
64 views

Data I/O operations for encrypted files

I need to implement a simple approach on a Linux system to encrypt/decrypt data and I would appreciate any feedback from you. Basically, I need to change a bit the behavior of the functions ...
1
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1answer
120 views

What is the most secure key expansion routine?

I am looking at G now, but is there a better, (in terms of security and speed), means by which a byte array can be expanded that doesn't involve another cipher, just a simple algorithm? I need to ...
1
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2answers
297 views

Are SSL/TLS used for maintaining data confidentiality?

In SSL/TLS, we use symmetric and asymmetric keys to encrypt the data. Does that mean that the keys are used to encrypt the data (preserve the integrity) or provide a secure channel for the data to be ...
1
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1answer
53 views

Is MAC algorithm same at both sender and receiver end

The MAC algortihm which is used along with a secret key to generate a MAC tag on the sender end ,is it same at the receiver end also who again uses a MAC algorithm to generate a tag? If yes, then how ...
1
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1answer
651 views

Is SHA related to AES or TLS in any way

I have been reading about SHA-2 family and I found a lot of in depth details, but I am confused about how it is related to TLS and AES. TLS encrypts data between server and client, but does it make ...
1
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1answer
83 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 ...
1
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1answer
82 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' ...
1
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1answer
96 views

public key delivery without third party

I am currently working on an anonymous P2P file sharing application and I am elaborating some already existing solutions. Some of them allegedly provide point-to-point encryption using RSA ...
1
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1answer
255 views

Whitening and randomness extraction

The Von Neumann randomness extractor is explicitly mentioned in the randomness extractor page of Wikipedia, but strangely enough that page does not contain any reference to whitening the results of an ...
1
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1answer
129 views

Rate my idea: is that a stronger GPG-like algorithm?

I came up with a simple idea but I don't know if it is really secure or not. I know that you shouldn't create any algorithm on your own. I'm just curious, that's all. Algorithm explanation: First ...
1
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1answer
193 views

Importance of salt when deriving an encryption key

I'm very curious to know this and a bit confuses too: Suppose, I have two files encrypted using AES-128bit with keys PBKDF2-derived from the same password and the same salt. If an attacker does ...
1
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1answer
91 views

Generate Finite Field power of g

consider the field $\mathbb{F}_{2^4}$, defined by using polynomial representation with the irreducible polynomial $f(x) = x^4 + x + 1$. Given element $g = (0010)$ as a generator for the field, How ...
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1answer
89 views

Public Key Cryptography: Diffie-Hellman Key Exchange

Please watch this video it's very short. If you already know cryptography and really good at it please start from 3:51. I didn't understand the step at 4:39, can someone here to explain? Why is ...
1
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1answer
105 views

How to adjust scrypt parameters for Moore's Law?

I have been examining the scrypt paper, and I noted the claims in table 1. For 10 random ASCII characters, the cost at that time for scrypt set to $(2^{14}, 8, 1)$ is estimated to be $175T/yr. ...
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1answer
193 views

SHA1 collision event probability after n iterations

There are String1 and String2 - some variables-strings. The probability of collision for different ...
1
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1answer
70 views

Fiat-Shamir security problem question

I am trying to understand the Fiat-Shamir identification protocol, but have a problem with understanding how this protocol is supposed to be save, even if you repeat it several times. I am using ...
1
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1answer
132 views

Are those RSA keys flawed?

I used rsa-json.native to generate RSA keys for a node.js application that will use secure-peer later to connect two clients with each other. Now I have 2 questions: In secure-peer/index.js I've ...
1
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2answers
254 views

Attack on a key-exchange,symmetric-key cryptography protocol

This is an exam question in Oxford 's Computer Security course: Here is the start of a protocol, based on a long-term secret key $k_{AB}$ previously shared between Alice and Bob, designed to offer ...
1
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1answer
137 views

Modulo properties of two prime numbers

I am supposed to prove that x = y mod (p*q) <=> x = y mod p and x = y mod q with p and q are prime numbers. It somewhat sounds reasonable to me, but unfortunately I don't have any clue how to prove ...
1
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1answer
117 views

Are formal methods used for cryptographic protocol design?

I decided to learn more about the application of formal methods to cryptographic protocols and found this interesting talk by Cathy Meadows at YouTube. After doing research about how people are using ...
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3answers
123 views

Encryption time in ECC

In RSA, encryption time is usually much less than decryption time due to having a small public exponent. Can this be achieved in Elliptic Curve Crypto (ECC)?
1
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1answer
107 views

How does this SSL-related flaw work?

I just saw a video at CNN in which it is claimed that, if the server isn't generating a random public key, the server can be hacked. First how HTTPS works… to be sure I’m on the same page: Server ...
1
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2answers
136 views

Understanding math behind RSA key derivation [duplicate]

I was reading through the key derivation for RSA. Here are the steps per wiki - Select strong primes $p$ and $q$ such that $pq = n$ $\phi(n)$ = $(p-1)(q-1)$ select $e$ such that $e$ and $\phi(n)$ ...
1
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1answer
74 views

Security assessment between $g^{a_ix_i+r_i}$ and $g^{x_i+r_i}$ [closed]

Imagine a tagging system whose security requirements imply to learn nothing from the tag about the encoded value. We consider a plaintext space $X \in \mathbb{Z}_p$ and a group $\mathbb{G}$ where ...
1
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1answer
68 views

How exactly are PRNG's used to encrypt material, and what makes one any more secure than the other?

I hope my question isn't as lazy as the title indicates. What I want to ask is how people literally integrate a PRNG with encrypting material. I wrote a silly little script in Python a while back ...
1
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1answer
163 views

Breaking RSA when some bits of one prime are known

RSA primes are 100 bit. You know first 80 bits of one of the primes. In this system, come up with an efficient way to decrypt the cipher-text. This was the question on my quiz. I'm not sure how ...
1
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1answer
89 views

Initialize the eight working variables SHA256

I have a little confusion in understanding explanation of SHA256 by FIPS a, b, c, d, e, f, g, h are being initialized as (this is what i don't understand) 2 . ...
1
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2answers
209 views

How to retrieve the plaintext of a substitution ciphertext?

So the other day, I was piqued by a ciphertext that was trivially encoded through substitution. Solvable only because we can use our eyes to determine word boundary word detection, etc. Trawling the ...
1
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1answer
70 views

On modeling a random oracle hash function which maps $\mathbb{G}_1 \rightarrow \mathbb{G}_2$

How can one model a random oracle hash function which maps $\mathbb{G}_1 \rightarrow \mathbb{G}_2$? (Assume $\mathbb{G}_1$ and $\mathbb{G}_2 $ to be additive and multiplicative groups of prime order ...
1
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1answer
52 views

How is an X.509 public key used for TLS?

Wikipedia's TLS article says: The client responds with a ClientKeyExchange message, which may contain a PreMasterSecret, public key, or nothing. (Again, this depends on the selected cipher.) This ...
1
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1answer
162 views

Can 64-bit “PRINCEcore” practically be brute forced?

There is a cipher called PRINCE proposed in ASIACRYPT two years ago. See the paper: “PRINCE – A Low-latency Block Cipher for Pervasive Computing Applications” The cipher divides the 128-bit key into ...
1
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1answer
141 views

How do you test the security of your cipher? [closed]

I got asked this question and I didn't know what to answer. How do you test the security of your cipher? What comes to my mind now would be to test it with famous attacks: padding attacks, ...
1
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1answer
65 views

Why does knowing the number of points on a curve help solve ECCDLP?

Perhaps, this is a really obvious question, but I am still having trouble understanding how this all fits together. Why is knowing the number of points on an Elliptic Curve helpful in cracking it? ...
1
vote
1answer
104 views

Timestamping using a hashed linked list and public known events

Let's say we have a timestamping scheme of the following characteristics, The hashes of the documents we are trying to timestamp are XOR'ed with "events" whose time of occurrence are very publicly ...
1
vote
1answer
145 views

What's the entropy of the output for Tiger Encryption?

I'm tasked to apply tiger encryption to my string(key). Does anyone have any idea how to find the entropy of the hex output by tiger encryption?
1
vote
1answer
256 views

Generalize the Merkle–Damgård construction for any compression function

I am trying to figure out this question: Generalize the Merkle–Damgård construction for any compression func­tion that compresses by at least one bit . You should refer to a general input ...
1
vote
1answer
68 views

Using beginning of TLS ecnrypted data to reveal secret [duplicate]

I have the following question about TLS security: Assume TLS-PSK protected HTTP with AES256-CBC cipher. When a TLS connection is established, client sends some encrypted data, where the plaintext is ...

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