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seen Sep 13 at 6:28

Sep
13
comment Regarding Key Strength with DES and Blowfish
To be secure you would want to E1 E2 E1, so an additional layer of DES encryption with the first key after the Blowfish layer
Sep
10
comment Is it possible to generate a secure permutation F over 32-bit integers even if F(0) … F(n) is public knowledge?
Just increment the counter till you get something without the non alphanumeric characters. You still get 3.5 trillion out of the 4.4 trillion to use, vs the 1.1 trillion for 40-bit, while saving 1 byte in the URL. 40-bit does allow an 8-bit internal structure however, which allows better s-boxes
Sep
10
answered Which block cipher mode(s) is most appropriate in these applications?
Sep
6
comment Is it possible to generate a secure permutation F over 32-bit integers even if F(0) … F(n) is public knowledge?
To satisfy my curiosity I created the 42-bit cipher since I had some of the building blocks already created. It will encode to 7 chars just like an Imgur URL. How secure I do not know, but it is similar to the HIGHT cipher in structure.
Sep
6
comment Is secp256r1 more secure than secp256k1?
Take a look at this: eprint.iacr.org/2014/368
Sep
6
comment Shannon confusion and diffusion concept
In more modern terms, I believe we apply confusion to mean a nonlinear transformation, and diffusion to be a linear one. Substitutions can be linear and not apply confusion.
Sep
5
comment Using SHA-256 with different initial hash value
NMAC/HMAC literally just hashes the key first to create the initial value, instead of using the key directly, and does it with 2 different keys in a wrapped structure. The security proofs require the hash to be a secure PRF, which is not completely fulfilled in practice.
Sep
5
comment What is the most secure key expansion routine?
Use a hash function like Keccak?
Sep
5
comment Base64 for a hash algorithm
I know of no cryptographic hash algorithm ever made that uses Base64 in the hashing process
Sep
5
comment Using SHA-256 with different initial hash value
@StephenTouset the benefit would be essentially the same as HMAC/NMAC provides, which is to change that initial hash value using a key
Sep
5
comment Is it possible to generate a secure permutation F over 32-bit integers even if F(0) … F(n) is public knowledge?
If you use a 36-bit permutation you can encode to 6 6-bit characters, which will fill the character domain much better, seeing as a 32-bit permutation will still require the same. A 42-bit one will allow a 7-bit internal structure and encode to 7 characters.
Sep
4
comment Is using SHA256 to extract entropy from a p-rand nonce a good way to create keying material?
I would personally do 119 bytes, that fills the 2nd block to capacity
Sep
4
comment Change Salt when Changing Password?
A rainbow table may also be made to target one specific high value target account, especially if the attacker knows the salt doesnt change...
Sep
4
answered Change Salt when Changing Password?
Sep
4
comment Statistical tests for pseudorandom permutations
I did something similar recently, a cipher with a 5-bit domain. I used a monte carlo like test, encrypting the prior ciphertext a billion times to see if it gets stuck in a cycle
Sep
3
comment Are SSL/TLS used for maintaining data confidentiality?
The channel is the data, could you be more specific? I cannot speak for SSL, just the current iteration of TLS.
Sep
3
answered Are SSL/TLS used for maintaining data confidentiality?
Sep
2
comment Is SHA related to AES or TLS in any way
If the HMAC diagrams do not make sense, you will need to gain a better understanding of how MD type hash functions work. Try reading the pseudocode
Sep
2
comment Is SHA related to AES or TLS in any way
"in what way different in TLS?" TLS uses different keys for client and server encryption and MAC, and this is generated from the shared secret. TLS specifies a PRF which makes use of HMAC and a seed to generate arbitrary data lengths, similar to a hash based KDF. Authenticated encryption modes only need 1 key per party.
Sep
2
comment Is SHA related to AES or TLS in any way
"The key used in HMAC is appended into the message". That is not quite how HMAC works. HMAC uses a hash algorithm internally, and the key changes the initial value of the hash, twice. This requires the key to be extended to the block size.