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I like crypto. Need I say more?


3h
comment Public key Issue - same key pair as existing one?
Related question or possibly even a duplicate.
3h
comment Public key Issue - same key pair as existing one?
It is very unlikely if everything is done properly (i.e., a good random number generator is used). Unfortunately, it has happened in practice. See the Debian OpenSSL RNG bug also this paper which details other issues found in practice.
Jul
25
comment Key Derivation from random salted seed, HMAC and HMAC based KDF
Note that you have another question on here with the exact same title.
Jul
25
comment Key Derivation from random salted seed, HMAC and HMAC based KDF
If you use the proper OS provided random number generators, then yes, they are good enough for encryption.
Jul
25
comment Key Derivation from random salted seed, HMAC and HMAC based KDF
To add to what otus says, most operating systems have built in random number generators. Most mobile device platforms (iOS and Android) have good random number generators built in. Why not just generate a 128-bit (or 192 or 256) random value and use that directly?
Jul
22
comment How can I solve this modular equation?
Compute the multiplicative inverse of 5 mod 13 (using extended euclidean algorithm). Then multiply 2 by that value. Viola, you have x.
Jul
22
comment RSA with modulus n=p²q
@Thor, I don't think CGFoX is planning on making the primes smaller to achieve the same bit size. Especially since the question specifies that using $p^2q$ would allow operations on a bigger $\mathbb{Z}_n$. That said, if the only benefit is a larger group, I would just pick larger primes to get the larger group personally (as you suggest).
Jul
22
comment Lowest number challenge scheme
@fkraiem remember though, you would have to always run the coin-flip (whether there was a tie or not), otherwise you leak whether or not there was a tie. My point is, things can get complicated.
Jul
19
comment Sectors of small data encryption
Pretty much every commonly used cipher today can meet your stated needs. Picking the best will require knowing your unstated needs. Who is the recipient? If it is someone other than yourself, do you have a secret key shared with them? Can you securely store a key?
Jul
18
comment Polynomial representation of the affine part of the AES S-box
Could you explain what l0-l8 are? I'm too lazy to read the paper right now.
Jul
18
comment Storing encryption key
Is this a stand alone app, or a client server app?
Jul
17
comment Are there any reasons for using SSL over IPSec?
@CodesInChaos, you are right. I am pinging the mods.
Jul
17
comment Given $g$, $b$, $g^{ab}$, is finding $g^a$ a hard problem?
In what group is $b^{-1}$ computed?
Jul
17
comment Are there any reasons for using SSL over IPSec?
Well technically from the first country to your home the connection would be encrypted with IPSec and SSL. When it reaches your home country, IPSec is removed and only SSL remains.
Jul
17
comment Are there any reasons for using SSL over IPSec?
Sure. Say I am in a different country and don't want my internet traffic snooped on. I can use IPSec to tunnel the internet traffic back to a server in my home country. Once that traffic leaves that server in my home country it will no longer be encrypted. So I use SSL to connect to, for example, a web mail server.
Jul
15
comment Decrypting an encrypted text out of order
Use a stream cipher
Jul
15
comment Decryption issue with self-coded AES-128
Richie, you are right. I realized that after I typed my comment and just left it. Feel free to roll back if you want.
Jul
15
comment CBC-MAC length extension attack with IV simulation
Are you able to capture many messages or just one? If so, do some of them have your account and the amount 1000000? If you could post example messages, that would be helpful.
Jul
15
comment Ciphertext indistinguishability (IND-CPA) for symmetric cryptography
Not if the IV is changing. That is why the comment I linked to is so important. An encryption algorithm is just a primitive, how are you actually going to use it? That is what you have to define.
Jul
15
comment Ciphertext indistinguishability (IND-CPA) for symmetric cryptography
This comment as well as the answers, etc might interest you.