157 reputation
7
bio website lvella.wordpress.com
location Brazil
age 27
visits member for 1 year, 9 months
seen Jul 21 at 20:40

Computer Science master degree student.


Jul
2
awarded  Curious
Sep
18
awarded  Commentator
Sep
18
comment Can I construct a feasible stream cipher out of HMAC and a secure hash algorithm?
Of what I know of stream cyphers, it is certainly possible to build a stream cypher out of a keyed hash function, like SHA-512 HMAC, Salsa20 is exactly that. The problem is that SHA-512 HMAC has such uneeded security guarantees (for the purpose) that makes it orders of magnitude slower than any stream cipher "by desing".
Sep
18
comment Can I construct a feasible stream cipher out of HMAC and a secure hash algorithm?
Could you use real pseudocode, because I have no idea of what this Data IV = [key SHA512]; means... or maybe try to explain the thing in english.
Sep
16
comment Integer factorization based password authentication
What is the problem with that salt shared with the user or public salt? I see it more as an user+site IV/nonce than a proper salt. In currently deployed schemes, if the attacker has read access to the stored passwords, it would see the salt. It is no secret, right?
Sep
16
comment Integer factorization based password authentication
Sorry. I understood now what you suggested... it really seems better.
Sep
16
comment Integer factorization based password authentication
Well, I believe that is the same reason the plain password is not stored on the server (or partially): if anyone can read the database, he/she will be able to login into the system.
Sep
16
asked Integer factorization based password authentication
Apr
25
comment Using the output of a stream cipher, how to guarantee the integrity of 4 bytes of data?
Well, that is my premise when I asked the question.
Apr
24
comment Using the output of a stream cipher, how to guarantee the integrity of 4 bytes of data?
I had realized the difficulty of finding the message boundary in case of corrupted stream, but I do terminate the communication in case of corrupted message. And since I am using a stream cipher, I can't easily recover from bytes inserted or removed from the stream.
Apr
24
awarded  Editor
Apr
24
awarded  Supporter
Apr
24
revised Using the output of a stream cipher, how to guarantee the integrity of 4 bytes of data?
added 45 characters in body
Apr
24
comment Using the output of a stream cipher, how to guarantee the integrity of 4 bytes of data?
In (message size x cipher output 2), x stands for multiplication...
Apr
23
comment Using the output of a stream cipher, how to guarantee the integrity of 4 bytes of data?
No, 4 bytes is the header, that tells the size of the following byte stream. But since the MAC is in the end, I want a simpler authentication mechanism to authenticate just the size.
Apr
23
asked Using the output of a stream cipher, how to guarantee the integrity of 4 bytes of data?
Feb
27
accepted Nonce role on stream ciphers
Feb
25
comment Nonce role on stream ciphers
But a key/nonce pair can generate a very long pseudorandom stream, I thought I could simply go on generating more and more bytes for the messages as long as the message sequence is not lost...
Feb
25
asked Nonce role on stream ciphers
Jan
26
accepted Using UMAC with stream cypher