# All Questions

3answers
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### Format Preserving Encryption for 32 or 64 bit plaintext values

I am looking for a Format Preserving Encryption implementation to apply to either a 32-bit or a 64-bit integer. It looks like AES/FFX mode is just what I need in terms of established security ...
1answer
286 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.
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1answer
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### MD5 update functions

In the hashlib module in python is a function called m.update() where m is a ...
1answer
140 views

### Encrypting twice with different modes?

I was using a SOCKS5 proxy today (tunneled through SSH) and I began to wonder what the effect of encrypting twice (TLS over encrypted SOCKS5 in this case) would have on the security of the transmitted ...
1answer
2k views

### What is the history of recommended RSA key sizes?

One can find up to date recommended key sizes for RSA at http://csrc.nist.gov/publications/nistpubs/800-131A/sp800-131A.pdf for example. In short it suggests a key size of at least 2048 bits. Is it ...
1answer
1k views

### How secure would HMAC-SHA3 be?

It would be possible to implement the HMAC construction with (draft) SHA-3, leading to HMAC-SHA3-224, HMAC-SHA3-256, HMAC-SHA3-384, HMAC-SHA3-512 (the last 3 digits are the output size $\ell$, where ...
2answers
219 views

### Database row level encryption scheme

I am wanting to secure some highly sensitive data in a database. This would mean that the data needs to be encrypted and remain secure for 100 years if it were to fall into adversary hands. I also ...
1answer
113 views

### Cryptography system that limits the length of the encypted message

I have two devices which communicate via sms. This communication should now be encrypted. The devices can only send messages with the lenght of 160 characters. So i am looking for an encryption ...
3answers
228 views

### Elliptic curve parameters

What's the meaning of 160 bit Curve in Elliptic curve ? or 192 or 224 or 256 and etc. And What is the standard for selecting this number of bit ? why they don't say 100 bit curve?
1answer
145 views

### I need to know number of encryption/decryption operations? [closed]

If i want to break quadruple DES (say EDED), what is complexity? Like for EDE, it is O(2^112).
1answer
60 views

### HMAC_DRBG Generate Process: requesting N bytes at once different from requesting N bytes in total?

Am I correct in assuming that HMAC_DRBG would return different results if I, e.g. first request 4 bytes followed by a request of another 4 bytes instead of asking for 8 bytes at once? It seems that ...
1answer
218 views

### blowfish ecb with openssl doesn't give the expected result

I do the following via the Linux CLI: ...
1answer
239 views

A long question here, but I really want to motivate why I'm confused. Consider the following attack on the Schnorr Identification Scheme. Alice chooses a random $k$, computes $\gamma = \alpha^k ... 1answer 288 views ### Compare two approaches for cracking RSA key I came across these questions while studying for a crypto course, does anyone have any ideas on how to answer these? (a) Random prime numbers of size 1536 bits are chosen to generate an RSA modulus ... 2answers 186 views ### Are LFSRs enough for this? Consider the following experiment: Let there be a machine which runs (ie. continually clocks) an LFSR of size (ie. number of bits)$b$, having a button that, when pressed, extracts the next$t$... 2answers 1k views ### How to better generate large primes: sieving and then random picking or random picking and then checking? I'm writing an RSA algorithm, and am wondering what is the best and/or usual way to choose the initial prime numbers (p and q). I know of two methods to achieve this, one based on a prime number ... 1answer 8k views ### How does TLS_FALLBACK_SCSV help? After reading through https://tools.ietf.org/html/draft-ietf-tls-downgrade-scsv-0, I could understand that this option is recommened for use when one has legacy SSL Servers which only support SSLv3. ... 2answers 165 views ### AES: Guess Password using the unencrypted text? I am using the same password for some encrypted files currently (I know this is bad practice, though), and I wonder whether an attacker could decrypt if one decrypted file fell into his hands. 1answer 176 views ### Encrypted read-only message queue I'm creating a prototype for a messaging queue with some custom logic (can't re-use any existing solution). One requirement is to have all messages encrypted. There are three classes of nodes ... 1answer 107 views ### Use of ElGamal encryption for signature generation If RSA (textbook RSA that is) generates a digital signature by using the sender's private key, couldn't any cryptosystem (the only two that come to mind are RSA and ElGamal) capable of asymmetric ... 2answers 271 views ### Output of a Feistel network with all “0” round function What is the output of an r-round Feistel network when the input is$(L_0, R_0)\$ and each round function outputs all 0s, regardless of the input?

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