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May
9
reviewed Approve Cryptographically secure keyed rolling hash function
May
6
comment Is $G$ a secure PRG?
You should specify what F is (I assume a pseudorandom function) and where k comes from.
May
6
revised Is $G$ a secure PRG?
added 26 characters in body; edited tags
May
4
comment Block cipher encryption of decryption with the same key
It depends on what you mean by "encrypt with a blockcipher". If you mean using a blockcipher in a secure mode of operation, then no, the probability of this happening will be negligible.
May
3
reviewed Leave Closed Is it true, that non-military cryptography appeared in 50's and 60's only thanks to leaks from the NSA?
May
3
comment PRF and hash functions
No, hash functions are only modeled as random oracles for proofs in the random oracle model. If we work in the standard model, a hash function is only assumed to be collision resistant. The key of a hash function stems from a technicality of defining collision resistance. The problem is that it is (almost) impossible to define collision resistance for a single function. Therefore collision resistance is defined for a function family, and the key is required to select a member of that family.
May
2
reviewed Leave Open PRF and hash functions
May
1
answered PRF and hash functions
Apr
22
reviewed Close Is less security required for a short stream cipher than for the AES enciphering of very long messages?
Apr
22
reviewed Reject How secure is AES-256?
Apr
16
reviewed Leave Open How can I convert numbers into prime numbers?
Apr
16
reviewed Leave Open Exchanging Keyspace and Message space in PRF
Apr
15
comment What is a 'secret key factory'? What precisely is it doing?
This question appears to be off-topic because it is about the inner workings of a particular java library. But to answer your question: What you are seeing is the Object ID being printed because you tried to print an object to the standard output. Check the documentation docs.oracle.com/javase/7/docs/api/javax/crypto/spec/… what you are looking for is probably the output of the getEncoded() method.
Apr
7
reviewed Looks OK Should we MAC-then-encrypt or encrypt-then-MAC?
Apr
7
reviewed Looks OK Should we MAC-then-encrypt or encrypt-then-MAC?
Apr
7
reviewed Leave Open Compression step of PGP
Apr
7
reviewed Leave Open What is h in this RSA variant?
Mar
18
revised Why concatenate the key a second time in HMAC?
added 9 characters in body; edited tags
Mar
17
reviewed Reject Randomness test question from FIPS 140-1 and comparison with 140-2
Mar
14
comment Is this a pseudo random function (PRF)? F(k,x) = f(k,x) - f(k,x-1)
@fgrieu This is getting way too long for the comments. But you have some basic misunderstanding about the proof technique here. IF the construction from the proof WOULD work against $f$, THEN the proof would lead to the conclusion that F'' is a PRF. But it does not.