0
votes
0answers
65 views

How to make a crypto-currency robust to 51% attacks?

For Example: In Bitcoin it is theoretically possible to double spend if you control > 50% of the computational power in the network. Also it is possible to apply "selfish mining" with far less than ...
0
votes
0answers
83 views

Any field in a PKI certificate where some text info can be stored?

I want to store 5-10 lines of Text Info in a PKI Certificate. All I want is that when using common tools like openssl command line or certutil from Microsoft, this text info should be displayed as is. ...
0
votes
0answers
94 views

m ∈ Zn \Z*n, RSA works but not secure

If you happen happen to have a message m ∈ Zn \ Z*n, RSA works but not secure. How likely is it going to happen? |n|=1024 bits |p| = 512 bits |q| = 512 bits.
0
votes
0answers
42 views

Encryption of numeric value using playfair

I am studying in CSE and in my recent exam paper, A question was asked as: Construct a playfair cipher for Plaintext: semester5 and key:technology. Generally as we are taught yet, there is no ...
0
votes
0answers
46 views

Private Set Intersection Polynomial Computation [duplicate]

I am trying to implement the protocol mentioned in Section 3.4 of “Efficient Robust Private Set Intersection” in Java. In the Second Step, the Client computes a polynomial of degree $n$ over the ...
0
votes
0answers
57 views

Plaintext patterns leaked based on single bit

Assuming that Elgamal is used as an encryption cipher, where lets say $p$ is 2048bit prime. Is it possible for an attacker to figure out $x$, a secret key, if any part of 2048 bits ciphertext and ...
0
votes
0answers
47 views

Key change and key derivation

there are two ways for key change: Key update and re-keying. Which of this methods use KDF (Key Derivation Function) for getting new keys.
0
votes
0answers
117 views

Going Blind, Group or Ring?

I have several problems approaching the following problem: Let's assume that we have Alice, Bob and Cathy. Alice wants to present a message to Cathy, showing her that someone else has signed it (Bob), ...
0
votes
0answers
76 views

Question Error Correcting Codes

Let $C$ be a code over the finite field $GF(2)$ with generator matrix $G$ and parity matrix $H$. Let $e+C=C'$ be a coset of code $C$. Let $S$ be a non-singular matrix and $H'=H\times S$. Finally, let ...
0
votes
0answers
68 views

Where can I find source code of a compiler that secures a circuit (or attemps to)? [closed]

In the paper “Multiparty Computation Secure Against Continual Memory Leakage”, on page 1239 under section “Using an LDS Compiler Instead of OCL Compiler”, the authors discuss why they decided to use ...
0
votes
1answer
100 views

Oracle DBMS_RANDOM algorithm?

Oracle DBMS offer builtin random number generator (pseudo to be accurate). DBMS_RANDOM is one of the available packages, it is however considered as insecure for cryptography. Do we happen to know the ...
0
votes
0answers
22 views

How to understand the Bilinear mapping with an example [duplicate]

An efficient bilinear map is given by $ e $: $G_{1}$ × $G_{1}$ → $G_{T} $. How can i prove this equation with the help of an example.
0
votes
0answers
34 views

In Merkle Damgard Constructoin, why do we add another block with value of number of blocks? [duplicate]

I'm trying to understand how can we find collisions, in simpler Merkle-Damgard constructions. consider my question as, what are the collisions for these cases of Merkle-Damgard constructions: we pad ...
0
votes
0answers
42 views

How to select parameters based on some condition

I am implementing a protocol for authentication where parameters need to be selected with $gcd(\mu,\phi)=1$ where $\phi=(p−1)(q−1)$. What is the best way to select the parameters while implementing
0
votes
3answers
356 views

Would it be possible to create a game where one would need to decrypt a simple encryption?

This might sound pretty weird, but I was thinking of a game a person could play alone with a pen and paper. I got this idea where the person would write a random four letter string on a paper, and ...
0
votes
0answers
27 views

Different between Shared Key and Common Key in DLP Application

What is the different between Shared Key and Common Key? Are they the same? Shared Key = Common Key?
0
votes
0answers
112 views

So what is quantum cryptography anyway?

I am having difficulty understanding quantum cryptography concepts. I've searched the internet and watched some videos on youtube explaining the topic, but it is still hard to understand how it works. ...
0
votes
0answers
34 views

Correlated or biased coin protocols?

There are a number of papers in the literature describing secure/fair coin flipping protocols. Unfortunately in my case, I am looking for coins that are epsilon-biased or epsilon-correlated. I am ...
0
votes
0answers
128 views

If H(m) = 0 for some m, how can a DSA signature be forged?

If we know for some message $m$ that $H(m) = 0$, how can we forge a DSA signature with only the public key? I got that $g^s*r = (g^x)^r$ where $x$ is the private key, but that's one equation with 2 ...
0
votes
0answers
38 views

Why doesn't this authentication protocol work? [duplicate]

I am a student taking a cryptography course so forgive me if this comes off as a silly question. This is an assignment question: Alice ------R--------> Bob Alice <-----[R]B------ Bob Alice ...
0
votes
0answers
221 views

Blum-Blum-Shub Cryptosystem

I am given $N$, which is Bob's encryption key. I was able to successfully factor $N$ into $N=p*q$. Alice encrypts a messages for bob and sends $a = [1,1,1,0,0,0,1,0,1,1,0,...]$ $b = 1545164156...$ ...
0
votes
0answers
217 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 ...
0
votes
0answers
83 views

becoming a cryptographer after math studies [duplicate]

after studying philosophy and being a philosophy teacher, I took back studies 4 years ago and I did a bachelor in maths. I'm in maths grad school now (I'm 32), and I would like to work in ...
0
votes
1answer
196 views

Why does WPA2-PSK use 4-way handshake instead of 2-way handshake

I don't seem to grasp why is the handshake for PTK in WPA2-PSK 4-way and not 2-way. Isn't it enough to just have these two steps: First party sends Nonce1 to the other party Second party sends to ...
0
votes
0answers
61 views

Example of CL PKC

I am trying to solve the example of algorithms of Certificateless Signature by manually and solving the mathematics of Algorithms but not succeed while doing mathematical calculations. Please ...
0
votes
0answers
42 views

Merkle-Damgard transform: necessity of the Length block [duplicate]

The Merkel-Damgard transform append the message length (in blocks) to the message itself and then computing the 'chained hash' algorithm. Does the last block (which contains the length of the ...
0
votes
0answers
29 views

Finding ECDSA public key from signature samples [duplicate]

How many plain ECDSA signature samples are needed to guess the corresponding public key from it like RSA? Otherwise, is it impossible to guess public key from ECDSA signature/encryption messages?
0
votes
0answers
72 views

hybrid PKE scheme CCA2 insecurity

I'm reading a paper here say: As we know, in hybrid PKE schemes XOR alone cannot perfectly hide challenge bit to the CCA2 adversary The author does not define hybrid PKE schemes. What is ...
0
votes
1answer
101 views

Why is appending the key to a mesage and then hashing that insecure if the hash isn't weakly collision resistant? [duplicate]

Suppose I have H(M|K) and that H is not weakly collision resistant. If I have a message mac pair (M,MAC), how is it possible to find another message mac pair (M2,MAC2)? My thinking for this problem is ...
0
votes
0answers
48 views

What is the default type of salt for encryptions in Heimdal Kerberos?

I am trying to figure out what the salting mechanisms are for various kinds of encryptions in Heimdal Kerberos. In section "4.11 Encryption types and salting" of the Heimdal Kerberos documentation it ...
0
votes
0answers
30 views

Using same keypairs for crypt and sign with elliptic curve [duplicate]

I asked my question on a mailing list ( http://www.metzdowd.com/pipermail/cryptography/2013-October/018061.html ) and i received many answers, which are confused me. So i try to ask here, it is ...
0
votes
1answer
104 views

Blind Signatures

The verification algorithm given in blind signature. Should it work for both Original message and the signature on it Blinded message and the signature on it. If yes, then how can we verify if ...
0
votes
0answers
73 views

Why is Merkle-Damgård construction insecure? [duplicate]

I've been reading about SHA-1. I read that SHA-1 is insecure as it uses the Merkle-Damgård construction and the Merkle-Damgård construction is — according to Wikipedia — susceptible to a variety of ...
0
votes
0answers
156 views

How to safely sign a 6 characters String?

I have to decide, whether a document, which I am given, was correctly signed by a private key. my Ideas is to sign the document id using RSA with the private key and to print the following onto the ...
0
votes
0answers
110 views

RSA vs El Gamal digital signature. Which is more secure? [duplicate]

I'm reading about the notions of security concerning digital signatures and I can't understand whether RSA is more secure than El Gamal digital signature. Well, they are both prone to forgery, but I ...
0
votes
1answer
59 views

PKCS#11: Which CKK_types are supported by CKM_PKCS5_PBKD2?

On Solaris there's a function pkcs11_PasswdToKey() which is a wrapper of C_GenerateKey(). I made a simple test and it turned out ...
0
votes
0answers
62 views

Strength of Combining Hash functions [duplicate]

If I combine two hash functions, what will the impact on the strength of the resulting function. If I combine in following way: H1*H2 (multiply) H1 + H2 (concat) H1 Xor H2 H1 (H2) EDIT: Lets say H1 ...
0
votes
0answers
42 views

NIST Standard for Advanced Encryption Standard Algorithm [duplicate]

Possible Duplicate: Advantage of AES(Rijndael) over Twofish and Serpent What is the reason of NIST why Rijndael choose as the Advanced Encryption Standard
0
votes
1answer
31 views

What is the exact purpose of length padding in Merkle–Damgård hash functions? [duplicate]

Is a length padding technique in a hash function used to avoid length extension attacks ?
0
votes
2answers
226 views

Reuse of a DH / ECDH public key

I was wondering whether it is safe to use the same DH or ECDH key pair in more than one key agreement, particularly if these public keys are in a public registry. These public keys could be used by ...
-1
votes
5answers
136 views

Symmetric encryption is no longer necessary?

Here is it: Symmetric encryption is no longer necessary, because all security services can be implemented with public-key cryptography. Moreover, in public key cryptography the operations for ...
-1
votes
3answers
218 views

Padding of Original Message in MD5

what should I do if my original message is greater than 64 bits? what is the process of padding in MD5? As described in Internet Security: Cryptographic Principles, Algorithms and Protocols, page ...
-1
votes
3answers
512 views

Encryption technique performance evaluation

I've come up with a light weight bit wise encryption algorithm and seems good. Ive tried it with text and image input. But I've the following questions I would like to ask What do you think of bit ...
-1
votes
3answers
14k views

Uncompress password protected WinRar file without password

I would like to know how to extract contents of the password protected WinRar file without the password. I have downloaded that WinRar file from a file hosting website and found out that it was ...
-1
votes
5answers
62 views

Why can't you decrypt an encrypted message with just the public key? [duplicate]

How does asymmetric crypto work? For example, if you use PGP in emails, you generate a private key that is known only to you and a public key, which is available to everyone. Is there a simple way ...
-1
votes
1answer
196 views

Does a playlist of songs or movies mixed together contain enough random enough for OTP key material?

Ok hypothetical scenario. Lets say I want to generate a lot of key material quickly for a one-time pad. This key material will be divided up and used for many different messages in the future. I ...
-1
votes
2answers
323 views

May the problem with DES using OFB mode be generalized for all feistel ciphers

There is a problem with using DES as the block cipher in OFB mode, eg: the feedback that goes back into the next round will be encrypted with the same key $k$ resulting back into the plaintext IV used ...
-1
votes
3answers
88 views

Could I use an hashing function for Symmetric encryption? [duplicate]

I know there are way better and more tested encryption methods, but I was wondering if the following code could be use for symmetric encryption? ...
-1
votes
1answer
168 views

How to bring little changes in DES algorithm

I thought of implementing DES modes of operation as a project...But my guide asked to change or to modify the DES algorithm in such a way to overcome drawbacks of DES...So is there any way to do ...
-1
votes
2answers
277 views

Shamir Secret sharing - Can share generator keep x values secret?

I'm wondering, in Shamir secret sharing, can generator of the shares, keep the x values which are used in evaluating the polynomial to obtain y values (i.e., the shares) secret, and whenever the ...

15 30 50 per page