# All Questions

343 views

### An Elliptic curve cryptography implementation which can be terminated

I'd like to have an implementation of elliptic curve cryptography along the lines of secp256k1 which is secure until some information is published after which it is broken. One idea would be to use ...
228 views

### Changing algorithms during encryption

Inspired by "Guarding against cryptanalytic breakthroughs: combining multiple hash functions", I am curious if there is a cryptographic reason to use only one algorithm during encryption. For ...
245 views

### How can I use Weierstrass curve operations with a=-3 for implementing operations for a=0?

I am working with golang's elliptic library. It implements functions on Weierstrass elliptic curves with $a=-3$. I need to make my own library that allows me to handle curves with $a=0$. I understand ...
431 views

### What algorithm does PGP use to encrypt email?

I know it uses RSA/DSA to create keys, but does it use that same algorithm for the actual cipher?
358 views

### How can two different passphrases unlock the same content?

I have heard that in enterprises it is common that the IT admin has a master passphrase that can unlock any content that an employee encrypts. It would be temping to think, that the IT admin's ...
180 views

### Are more complex algorithms easier to break with timing attacks?

Is there a point where increasing the complexity of an encryption algorithm will make it easier to break using a timing attack? Or is there no connection here at all?
24k views

### How can I generate large prime numbers for RSA?

What is the currently industry-standard algorithm used to generate large prime numbers to be used in RSA encryption? I'm aware that I can find any number of articles on the Internet that explain how ...
302 views

### How can I store confident data with OpenID?

I want to make a system that needs to store some confident user information in a database. I intend on using OpenID for user authentication. I would like encrypt the data in a way that it can only be ...
9k views

### AES in ECB mode weakness

In a project that I'm currently working on, we are encrypting some data using AES with ECB mode in a database. Each piece of data being encrypted is very small, no more than 10 characters long. Very ...
4k views

### How can a random salt for a hash function work in practice?

I understand the theory behind the use salts in hash functions, but when I see it implemented, the implementations always generate the salt on the fly and the salt appears to be different for every ...
3k views

### How were the DES S-box values determined?

It seems like the S-boxes in DES have essentially random values. How were these chosen?
517 views

### Key Length & Hashing

I need to use a hash function to generate a 128-bit key for a symmetric cipher. The specific cipher is from the eStream portofolio, called Rabbit. I am using the SRP protocol for authentication (a ...
3k views

### Does the generator size matter in Diffie-Hellman?

For the Diffie-Hellman protocol I've heard that the generator 3 is as safe as any other generator. Yet, 32-bit or 256-bit exponents are sometimes used as generators. What is the benefit of using ...
8k views

### RIPEMD versus SHA-x, what are the main pros and cons?

RIPEMD is a family of cryptographic hash functions, meaning it competes for roughly the same uses as MD5, SHA-1 & SHA-256 do. The Wikipedia page for RIPEMD seems to have some nice things to say ...
308 views

### Are there reference implementations of ECQV implicit certificates?

I am interested in exploring ECC implicit certificates, specifically using the ECQV protocol. While the actual implementation would not difficult to perform using building blocks provided by most ECC ...
4k views

### Why has the RSA factoring challenge been withdrawn?

Wikipedia states that RSA challenge has been withdrawn. Does it mean that an efficient factoring algorithm is "just around the corner"? or are there some other reasons? If the challenge was still ...
5k views

### What is the “Random Oracle Model” and why is it controversial?

What is the "Random Oracle Model"? Is it an "assumption" akin to the hardness of factoring and discrete log? Or something else? And why do some researchers have a strong distrust of this model?
2k views

### How well does scrypt perform on different architectures / OSes?

The scrypt algorithm seems to be a prominent feature in the "CPU friendly" Bitcoin clones for the proof-of-labor part. I've heard claims that it's relatively slow on Windows and/or Intel compared to ...
1k views

### Encrypt-then-MAC Confidentiality, Integrity and Authenticity

Does Encrypt-then-MAC provide equal confidentiality, integrity and authenticity as other constructs such as EAX? If yes, how do I go about using it? My current understanding is: E = ...
171 views

### Generating non-repeating N-bit IVs, which are indistinguishable from randomness

I'm implementing a protocol which needs a 64-bit IV for every encrypted packet. The cipher in use (AES-GCM, more or less as specified in RFC 4106) does not require that these IVs are random, only ...
3k views

### How do other, non-RSA algorithms, compare to the PKCS #1 standard?

Arguably the PKCS suite of standards have a profit-oriented bias as they are promoted by RSA and promote their algorithms over others in the form of RFCs and other means. I'm considering the ...
180 views

### When is an asymmetric scheme considered broken?

Does the following quote imply that valid encrypted data can be created and decrypted by someone other than the owner of a private key: An asymmetric encryption scheme is considered to be broken ...
187 views

345 views

### Analysis of Repeatedly Enciphered Plaintext using Same Algorithm / Key

Please forgive the impracticality of this question, but I'm curious about the behaviors of encryption algorithms applied to their own output. Suppose I have an encryption algorithm E and (using the ...
786 views

### UMAC: to what extent is it in use today?

Inspired slightly by the Encrypt-then-MAC question. The most obvious message authentication code is probably HMAC or RFC 2104 which is basically a hash of the input, an xor with a key... you get the ...
172 views

### Is a changing public truecrypt container secure?

I have a Truecrypt container which I want to synchronise between computers (i.e. different people, that I want to share the data with). If I used Dropbox for synchronisation and someone downloaded ...
306 views

### How is the MJH double-block-length hash function constructed?

I'm looking for information on the MJH double-block-length hash function, but the best free source I could find is the diagram on page 18 of Efficient hashing using the AES Instruction Set (submitted ...
714 views

### How do I construct a 256-bit hash function from 128-bit AES?

I would like to generate a 256-bit hash on a microcontroller that has a 128-bit (only) AES engine. How can I construct a 256-bit hash function from a 128-bit cipher?

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