1
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1answer
42 views

Using HMAC to secure a “widget”

Let's say I have a web "widget" that a customer could include on their website. They would include the widget by adding an iframe that points to a URL on my site. I want to ensure that my widget can ...
1
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0answers
51 views

When do I need to renew keys for Salsa20 or HMAC?

I currently have a system which uses two keys sourced from a single key subjected to HKDF. One key is used in the Salsa20 stream ...
1
vote
0answers
104 views

Pohlig-Hellman exponentiation block cipher

Let $G$ be a group of order $n$ and let $e,d$ be integers such that $ed\equiv 1 \pmod{n}$. Then the exponentiation maps $x \mapsto x^e$ and $y \mapsto y^d$ are inverse maps on $G$. These maps give us ...
1
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0answers
74 views

Is it possible to modify SSL handshakes to enable PFS while still using RSA during the handshake?

I know we could possibly be using DH key exchange, that would enable PFS. However, what if we make modifications on our SSL 3.0 handshake such that the only cipher we use is RSA for the achieving PFS? ...
1
vote
0answers
94 views

Where can I find examples of ECC implemented in VHDL?

I am looking into implementing ECDSA signature and ECDH key agreement in a Xilinx FPGA. All the examples I have found of VHDL implementations skip over how to construct the low level ECC primitives ...
1
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0answers
58 views

Can you provide an example in relation to Hidden Field Equations Multivariate?

I'm reading about Hidden Field Equations Multivariate scheme. My lecture states that the central map is a univariate polynomial $$P(X)=\sum_{i=0}^{r-1}\sum_{j=0}^{r-1}p_{ij}x^{q^i+q^j} \in K[X]$$ ...
1
vote
0answers
95 views

Is there any analysis of freebsd's “geli” encrypted geometry provider?

I've done a few obvious searches on google and google scholar and not turned up any security analysis of FreeBSD's geli. Is there some out there, or has it gone unanalyzed since its introduction ...
1
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0answers
157 views

What is the chance of a collision when using SHA-3?

I currently am writing a web app and am using two random hashes that are before and after the string and are both 50 char long (alphabet, numbers, and special chars). ...
1
vote
0answers
89 views

$\phi$ function in Dual_EC_DRBG

I am trying to understand the operation of the Dual_EC_DRBG. I'm reading the formal specification (SP 800-90) and can't seem to find a definition of the $\phi$ function used throughout the definition ...
1
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0answers
139 views

How good is the RandomPool generator in Crypto++ library?

How good is the RandomPool generator in Crypto++ library? I never heard of it before… I wonder if there is a Fortuna C implementation that I could use in an Objective-C project. Also: How secure is ...
1
vote
0answers
65 views

How can user privacy be preserved in certificateless cryptography?

In certificateless cryptography, how can a user preserve his privacy from Key Generation Center? If the KGC becomes malicious, how can the user's privacy be preserved? I read "Privacy-Preserving ...
1
vote
0answers
35 views

TCR hash functions from MD5

I'm reading Collision-Resistant Hashing: Towards Making UOWHFs Practical (pag. 10 and 11) and here say The most direct way to construct a TCR hash function is to key a function like MD5 or SHA-1. ...
1
vote
1answer
94 views

Reusing PGP key when generating SSL Certificate Authority?

Does it make sense to reuse some of the keys from my PGP (gnupg, gpg) keyblock when generating my own SSL Certificate Authority (a toy one for myself and a few web services of mine)? In an ideal ...
1
vote
0answers
107 views

Design requirements for a keyed hash function?

I am actually preparing for a cryptography exam, and I found a question asked by the professor in the class, below are the lines that I copied from the slide : Example: Let $Ek$ be the encryption ...
1
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0answers
114 views

Best group if one wants the discrete log problem to be hard?

Suppose one is implementing a cryptographic scheme over a group where one needs the discrete logarithm to be hard - what is the recommended group to use? I'm looking for a group where calculations are ...
1
vote
1answer
86 views

Upper bound Linear Feedback Shift Register

It is clear that when we have any output stream $x_0,x_1,...$ produced by linear feedback shift register than this output has to be periodic. Now I was wondering if we can find an upper bound for ...
1
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0answers
43 views

AES and Known-plaintext attack [duplicate]

Can you help me to finding some papers that shows AES is secure against known-plaintext attack?
1
vote
1answer
84 views

Bit commitment with 1-out-of-2 oblivious transfer

I know a protocol for bit commitment using regular OT (Bob has 1/2 chance of learning the bit Alice transferred to him) which goes like this: COMMITMENT PHASE Alice chooses a bit $b$ For ...
1
vote
1answer
93 views

Creating a secure key

Imagine that your lecturer and the undergraduate office have conducted a key exchange protocol after which both of them hold the string $X$. Yet, it is possible that a curious student sitting next to ...
1
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0answers
37 views

Computing A, B given A+K and B+K [duplicate]

In his writeup of the Solitaire keystream generator algorithm, Bruce Schneier warns not to use the same key for two different messages: The first rule of an output-feedback mode stream cipher, any ...
1
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0answers
66 views

Generating a valid signature on El-Gamal without knowing the private key

Suppose we are given $p$, the large prime, $g$ which is the primitive root for $p$, $b$ which is calculated as $b=g^x$ mod $p$ where $x$ is the private key and $0<x<p-1$. Also suppose we know ...
1
vote
0answers
93 views

What scheme will allow merging and splitting the result of a function?

I am wondering if it's possible to have a scheme as follows. Here is the scenario: we have a set of objects (e.g. strings) {O1, O2, ..., On} we have a set of users {U1, U2, ..., Um} each user asks ...
1
vote
0answers
81 views

Could MITM securely identify identity?

Consider protocol like QUIC or MinimaLT which are essentially layer4 replacement for TCP/UDP (riding on top of UDP currently because of fear of random firewalls dropping new L4 protocol). From crypto ...
1
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0answers
36 views

MD Construction Doesn't Propagate TCR

I'm reading a proof of the proposition of CollisionResistant Hashing Towards Making UOWHFs Practical Suppose there exists a compression function $F: \Sigma^k\times\Sigma^{c+m'} \rightarrow ...
1
vote
0answers
54 views

Perfect Forward Secrecy in MTI/A0

Would the property of perfect forward secrecy still be achieved in MTI/A0 for a session key that was established between C and D when one LL-key aD is revealed so that both LL-keys aC and aD are ...
1
vote
1answer
149 views

How can an encryption scheme be indistinguishable with multiple messages but vulnerable to an adaptive chosen-plaintext attack?

In order to be indistinguishable with respect to multiple messages, wouldn't the scheme need to be nondeterministic? How would this then possibly be vulnerable to an adaptive CPA?
1
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0answers
126 views

About Elliptic Curve ElGamal, 3 simple problems I have trouble with

In Elliptic Curve ElGamal, why are a=b=1 always legal for primes whose lengths are no shorter than 11(2) bits long? Is there any reason why the Point at Infinity can always be encoded as (0,0)? ...
1
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0answers
130 views

Please explain Pairing based Cryptography with numeric example [closed]

I read concept of Pairing based Cryptography. But while trying understand the concept by doing mathematical calculation, I am facing much problems. So, could you please explain Pairing based ...
1
vote
0answers
160 views

Factoring large numbers

I am trying to factor few integers that are each between 115 and 135 digits long. I have just, little over a month ago, began my study of Cryptography. I was wondering if anyone knew of any efficient ...
1
vote
0answers
112 views

How to develop a public key cryptosystem based on a hard problem?

Recently, I found a function that is performed on a sequence to return another sequence. All known algorithms for finding the input, given the output are of exponential complexity. I want to propose ...
1
vote
0answers
45 views

Can you help me understand this strange implication direction in security reduction for OAEP 3-round?

I'm reading the paper OAEP 3-round, where they introduce a 3-round version of the OAEP (which originally used only two rounds). However, in their security statement for this construction (Theorem 4 ...
1
vote
2answers
98 views

Is it possible to decide the base of a discrete logarithm?

Given $R$, a prime $p$ and two bases $g_1$ and $g_2$, is it possible to decide if $R = g_1^r$ mod $p$ or $R = g_2^r$ mod $p$ without knowing $r$?
1
vote
0answers
103 views

Can keys from Bitcoin's Hierarchical Deterministic Wallets be correlated (reducing privacy)?

I'm trying to understand if the feature "Hierarchical Deterministic Wallets" in Bitcoin allows for complete privacy of all derived keys, and if any of those keys can be associated with each other ...
1
vote
0answers
138 views

Diffie-Hellman exchange

So for a Diffie-Hellman problem, I am given the prime $p$ for the Diffie-Hellman exchange. I am also given $g$, secret number for machine as $A$, secret number for station as $B$, a Diffie-Hellman ...
1
vote
0answers
59 views

Partial encryption of a file?

I want to partially encrypt a large block of data using AES. Meaning: given plaintext[0:1100], I would like to encrypt ...
1
vote
0answers
109 views

Cryptanalysis not based on method used to encrypt? [closed]

When doing cryptanalysis on RSA or something number theory based, there are various attacks that all seem to involve number theory (Wikipedia: RSA_(algorithm) ~ Attacks_against_plain_RSA). Similarly, ...
1
vote
1answer
150 views

Hill Cipher - Unknown plaintext attack, known key [duplicate]

I was wondering if I have the key and the encrypted Hill Cipher message(s). I can definitely figure out the charset involved. But the order is missing. Assuming that I use 37 modulo or higher. How ...
1
vote
0answers
125 views

PGP encryption options

I recently began using PGP desktop and found several options for my encryption capabilities. Which of these (AES, Cast, Triple DES, TwoFish, IDEA) is the most recent, firstly, secondly may the NSA not ...
1
vote
0answers
135 views

Are any Certificate Authorities using 4096 bit keys for their intermediate and root certificates? [closed]

Are any Certificate Authorities using 4096 bit keys for their intermediate and root certificates? I know you can, of course, use a 4096 bit key for your server certificate, but I usually see 2048 bit ...
1
vote
0answers
192 views

Does BouncyCastle (for ECC) resist timing attacks?

I need to extend the TLS protocol to be able to use other key exchange scheme based on elliptic curves. I am planning to use BouncyCastle's implementation in Java and in .NET. I am worring about ...
1
vote
0answers
456 views

Decrypting a message without the private key using CRT

I am given 5 different encryption modulus, $N$, each ranging from 78 to 88 numbers long. Then for the encryption exponent, each has the same which is 5. Then I am given 5 different encrypted messages, ...
1
vote
0answers
216 views

Understanding elliptic curve encryption

I'm having a hard time understanding the elliptic curve encryption. One thing thing I don't understand is listing all the points on the curve (mod p). Suppose I have the following elliptic curve: y^2 ...
1
vote
0answers
86 views

Career advice for our readers [closed]

I am a first year math PhD student with work experience and an MS in math. Do you have any advice regarding internships involved with cryptography and other mathematics other than the NSA? Thanks.
1
vote
0answers
126 views

How to perform benchmark of block/stream ciphers?

I would like to perform some benchmarking of different block and stream ciphers for general data (lossless and lossy data) encryption and decryption (with focus on power consumption). To get general ...
1
vote
0answers
49 views

How does Dissent protect against Sybil Attacks?

Dissent claims to be able to be resistant to Sybil attacks. Dissent seeks to offer accountable anonymity, giving users strong guarantees of anonymity while also protecting online groups or forums ...
1
vote
0answers
55 views

Can you help me understand this “Message Modification by Meet-in-the-Middle” related to Tiger Hash?

I found this paper that explains how to attack a reduced round tiger hash, but I'm having a hard time understanding some of the mathematical notation. Could someone explain the section "Message ...
1
vote
0answers
50 views

Algorithm for sharing secret information with redundant keys [duplicate]

I have an information that I would like to encrypt and give it to someone else. I would like to encrypt it using N separate passwords (say 5) and give each password to some other persons. However the ...
1
vote
0answers
38 views

one-time key, zero IV in stream cipher (e.g. AES-CTR) [duplicate]

Say I am using a random key to construct a stream cipher with, say, AES in CTR mode, which will never be used to encrypt more than one data stream. Is there any advantage, no matter how small, to ...
1
vote
0answers
228 views

RSA Attack with some known values

There is an RSA implementation which I need to attack to get the encrypted messages. Some of the values are known. Plain text value for input. So if I enter a message, say it "A", the plain text is ...
1
vote
0answers
66 views

LogSpace Merkle Traversal

I am studying LogSpace Merkle Tree Traversal algorithm in "Post Quantum Cryptography". I don't understand the Table 1 on page 58. My question is: Why within of the $2^h$ rounds for $NEED_h$ exist ...

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