0
votes
0answers
27 views

implementation of digit serial architecture

I am working on architecture of SIMON cipher where I have to use either bit serial, parallel or digit serial to implement the algorithm for each round function and also for sub-key generation. So I ...
2
votes
1answer
99 views

Given only RSA public key parameters, what security issues might I be able to detect?

I'm attempting to automate some checks against a large list of .NET assemblies, and want to include a test to see if the RSA parameters used to sign the assemblies are sensible. However, since I don't ...
2
votes
2answers
206 views

Why do we need to hash both the message and the $h$ value in ElGamal signature?

The professor left us a question on ElGamal signatures: Given the hash function $H$ and message $M$, choose a random $r$ and compute $h=g^r$ and $H(M||h)$. Show that, if $H(M)$ is used instead of ...
2
votes
1answer
40 views

Salting in asp.net?

I have spent the past hour reading up on salting and still don't understand how it is achieved. Forgive me if im wrong, but the way I am thinking of salting is, storing an ArrayList of random strings ...
1
vote
1answer
58 views

RSA signatures without padding

Suppose I have a message $M$ for which I generate an RSA-2048 digital signature as follows: $H = H(M)$, $H(M)$ being the SHA-256 of the message $M$ $S = H^d \bmod N$ Assume $N = pq$ is properly ...
2
votes
3answers
78 views

Are there transitive ciphers (either symmetric and asymmetric)

Say Alice has information that's already encrypted with Bob's key. She wants Bob to decrypt it without knowing what he just decrypted. So she encrypts it with her key and sends it to him, he decrypts ...
3
votes
1answer
52 views

Is there any good reason to chain HMACs in this manner?

I am looking at some decompiled Java code from an Android app. As a security measure, a signature is passed as a parameter to a number of JSON requests. The method that generates the signature is as ...
27
votes
4answers
4k views

How are primes generated for RSA?

As I understand it, the RSA algorithm is based on finding two large primes (p and q) and multiplying them. The security aspect is based on the fact that it's difficult to factor it back into p and q. ...
0
votes
1answer
51 views

How are messages from server secured when using SSL certificate

In case of using SSL the certificate server has a primary key and a public key that is published to all clients - as far as I understood. So in this case when message is encrypted by public key (on ...
2
votes
1answer
134 views

Is this variant of SRP useful?

I'm interested in using a modified form of SRP as a peer-to-peer authentication method. Since neither side is acting as a host, one of the primary design goals for SRP (that the client doesn't need ...
5
votes
1answer
82 views

What is degree of randomness in individual bits of MD5 hash?

I am researching on Hashing Algorithms and would like to know if we take individual bits of MD5, say we take first 8 bits or any random 8 bits of MD5 then what is the randomness probability of having ...
13
votes
1answer
793 views

Mapping points between elliptic curves and the integers

My primary question is: Is there an easy way to create a bijective mapping from points on an elliptic curve E (over a finite field) to the integers (desirably to $\mathbb{Z}^*_q$ where $q$ is the ...
3
votes
1answer
50 views

Why recently Edward curve formulas being developed that deviates from unification?

Edward curves were considered initially because it provides a unified formula for both doubling and addition, thus having inherent side-channel resistance. But a lot of work has been done recently ...
1
vote
1answer
44 views

sha256_hmac for session keys using a counter

I need to generate some session keys from a master key that was generated from an ECDH key exchange. The master key is 256 bits and I need 256 bit sessions keys. Is it safe to use SHA256_HMAC with ...
0
votes
1answer
213 views

Blowfish ECB mode: Tools for known-plaintext attack?

I'm currently dealing with multiple blowfish-encrypted files that share the same key. All are encrypted using ECB mode judging from their appearance. I don't know what the key is but I know 64 byte ...
3
votes
1answer
119 views

One cipher to rule them all?

I learned from Dan Boneh's course that many cryptographic primitives (prngs, stream ciphers, hashes, hmac, key derivation functions) can be built from just one a block cipher or PRF. For example, the ...
5
votes
1answer
95 views

Why have round constants in hashes?

This may seem like crypto 101, but why do hash functions like SHA2 and Whirlpool have round constants that are absorbed into their respective states? I can understand that in a cipher you need some ...
5
votes
1answer
143 views

Difference between “ECDH with cofactor key” and “ECDH without cofactor key”?

I need to use “ECDH with a cofactor key” for generating symmetric key. I have a fair idea on how ECDH works, but I don’t understand the cofactor part. What is the difference between ”ECDH with a ...
3
votes
2answers
56 views

Does AES(x || x) provide secure message authentication when message fits in a single block?

Suppose I have x = <64 bits of data>. I build a 128 bit block $P = x || x$, and transmit a message $M = AES(K, P)$. The receiver has the same $K$. The ...
0
votes
1answer
98 views

How to compute accumulated values in bilinear map accumulators

How to compute $ g^{1/(e_1+s)}$, where $g$ is the generator of group $\mathbb G$, and $e_1$ and $s$ are keys? I know only $s$ and $g^{e_1}$, not $e_1$. $\mathbb G$ has prime order for some prime $p$ ...
1
vote
0answers
45 views

How far is public-key crypto involved in “banking world”? [closed]

I would like to know how public key cryptography is used in the banking world. I am not looking for big details, but for example: Are banking card embedding a private key used for signing ...
0
votes
0answers
30 views

Encrypt with K1, K2 and decrypt in opposite with K2, K1 [duplicate]

When using symmetric cipher, does the following statement holds: E(x, k) means encrypting x with key k in ECB mode ...
0
votes
1answer
65 views

How to crack SHA256 only letters

I recently created a program that hashes a password using SHA256 and potentially using salt. How can I crack that if I know that the password only contains lowercase letters?
-1
votes
0answers
8 views

How does a CA send a digital certificate? [migrated]

I would like to know after approving the Certificate signing request, does the Certificate Authority send the Digital certificate to the applicant by converting the digital certificate to PEM format ...
0
votes
0answers
23 views

RSA-PSS salt size in certificate

In RFC 4055, the signature RSAPSS algorithm has the following ASN 1 parameters: ...
0
votes
0answers
33 views

one complex password as a “seed” for localy generated per-service passwords

I've stumbled upon a project that suggests a way of having to remember one password, from which a “per-service password” could be generated by salting the service name using scrypt. What could be a ...
1
vote
2answers
2k views

ECDH VS. DH benchmarking in JAVA

So basically my problem is the odd result i get when measuring the time it takes to generate a ECDH key in java vs. the time it takes to generate a DH key. I compare the time it takes to generate: ...
2
votes
1answer
78 views

Key exchange using ECDH vs ECIES

I'm a beginner to ECC crypto programming. Does any one explain to me the difference with using ECDH for shared key exchange and use of ECIES by encrypting shared key with the public key of the ...
9
votes
1answer
2k views

What are the advantages of a static ECDH key?

What are the advantages of using "static-ephemeral ECDH" over "ephemeral-ephemeral ECDH"?
0
votes
1answer
62 views

Why we need ECDSA when we have ECDH?

ECDSA and ECDH give us the following methods: ...
2
votes
1answer
366 views

openSSL ECDH private key size

When you are using a named curve like P-256 in openSSL, is there any standard key size for ECDH private key keys? If you look at the ec_key.c file in the openSSL ...
1
vote
1answer
32 views

Can I use an ECDH Shared Secret from the same Private / Public Key Pair?

I'd like to know if using the ECDH shared secret of a static EC Private Key with it's own corresponding static EC Public Key causes a problem / weakness. (edit) not asking if it's ok to re-use the ...
1
vote
0answers
42 views

RSA_DH vs ECDH implementation

In ECDH protocol is possible, naturally, to use the same algorithm for calculate a secret key for both communication parties (Alice and Bob for example). It is possible to design also a same algorithm ...
2
votes
2answers
213 views

ECDH anonymous key exchange to avoid PKI

I want to use TLS to encrypt the communication between peers in a P2P network. Each peer has a well known 256bit peer identifier (the public key of a 256bit elliptic curve keypair). Both peers need ...
4
votes
1answer
331 views

EC ElGamal versus static+ephemeral ECDH

A client application needs to encrypt a UDP datagram for a server with known EC public key $P$. Performing a full ECDH key exchange would defeat the benefit of using UDP as a connectionless protocol. ...
1
vote
2answers
457 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 ...
10
votes
1answer
4k views

ECDSA vs ECIES vs ECDH

Recently I started studying Elliptic Curve Cryptography and I just loved it. I want to transfer some big data (like 3KB), What is the best method, ECDSA, ECIES, or ECDH (and why)? I am confused, how ...
3
votes
2answers
105 views

ElGamal against chosen ciphertext attacks

In Hoffstein, Pipher, and Silverman's book An Introduction to Mathematical Cryptography, the authors make the following remark: An attack in which Eve has access to an oracle that decrypts ...
2
votes
2answers
90 views

Are all stream-ciphers IND-CPA?

A stream cipher usually generates a stream of pseudo-random bits which get XORed with the plaintext to form the ciphertext. The stream is generated using a given IV / nonce and a secret key. CTR-mode ...
0
votes
1answer
57 views

How hard is it to recover $p$ if I can get $h(p) \oplus h(p^*) \oplus r$ and $h(r)$?

Assume that $h:\{0,1\}^* \rightarrow \{0,1\}^\lambda$ is a cryptologic hash function, $r$ is taken randomly from $\{0,1\}^\lambda$, $p$ is a low-entropy password and $p^*$ is a guess. Now we get $h(p) ...
0
votes
0answers
32 views

Clarify EC point addition and multiplication

Please clarify the below doubt regarding EC point addition and multiplication: $P$-Generator Point; $a$ and $b$ are integers; $X$ and $Y$ are EC points, defined as follows: $X = (a*P) + (b*P)$ $Y = ...
1
vote
1answer
121 views

IND-CPA Security

Given a key $K$ (the key is fixed) and a nonce $N$ (changes from one message to another) Using a secure Key derivation function (KDF) such as the ANSI-X9.63-KDF with SHA-1 option to derive a key for ...
4
votes
1answer
137 views

Parallelization of CFB mode encryption and decryption

While reading Evaluation of Some Blockcipher Modes of Operation by Rogaway (someone just linked it somewhere), I noticed two claims about CFB that I'm not sure I understand: Regarding whether CFB ...
2
votes
1answer
78 views

Diffe-Helman Exchange result is always 1

I watched a video on Khan Academy explaining the Diffe-Hellman exchange. When I try to do an example problem, I get 1 all the time. Does the generator and prime modulus (or base on Wikipedia) have to ...
1
vote
0answers
69 views

Where can I find names for cryptographic notation I don't recognize?

I'm new to this space and find myself stumbling over come cryptographic/mathematical notation. Search engines are not very helpful when copying and pasting Greek letters. Is there any reference that ...
6
votes
1answer
826 views

Diffie-Hellman Parameter Check (when g = 2, must p mod 24 == 11?)

I'm adding some Diffie-Hellman groups to a program as specified in RFC 3526, More Modular Exponential (MODP) Diffie-Hellman groups for Internet Key Exchange (IKE). When I test some of the group ...
0
votes
1answer
92 views

Diffie Hellman Exponentiation Implementation Problem

im trying to work on key agreement schemas on embeded systems. for diffie hellman, ive written a 256 bit multiplication, on AVR core it takes about 2 seconds on 1Mhz frequency, lets say my algorithm ...
1
vote
1answer
38 views

Degenerate discrete logarithm in binary field

Given a field $\mathbb{F}_{2^n}$, are there any choices of primitive element $g$ that make the discrete logarithm easier for that generator? That is, are there any degenerate cases? For example, if I ...
8
votes
6answers
309 views

Mutual verification of shared secret

Is it possible to develop a scheme where two parties, unsure if they have the same secret, can verify that the other does or does not share the same secret, without one party being able to cheat and ...
-1
votes
1answer
29 views

different feistel words in key size

I have confusion on Feistel word in key size. Means, "what is the meaning of key size with different feistel word ?" What does m=2,3,4 represent? Where m represent different size of feistel word or ...

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