2,563 reputation
622
bio website
location Netherlands
age 40
visits member for 2 years, 4 months
seen 1 hour ago

Java and security expert with over 10 years of experience with the language and with the practical application of cryptographic protocols - including the design of protocols within international standardization bodies. Creator of a heavily used common criteria certified product. Over 30 years of experience with computers. Likes kids, cats, reading, movies and several sports.


1h
comment How can I generate a brief (100) stream of random numbers, not using the computer or throwing dice?
You may not intentionally cheat, but just be compelled to round off to e.g. half centimeters. If you do a lot of measuring, you will notice that this is quite a strong tendency. Besides that, a long jump requires a lot of equipment to be in place, and 100 jumps are not healthy. Gosh, you were not joking.
1h
comment HMAC definition by using only one key
Welcome to crypto, Snox.
1h
comment How can I generate a brief (100) stream of random numbers, not using the computer or throwing dice?
Too easy to measure incorrectly - people are bad measurers, they tend to cheat, round off, etc. Besides, we are cryptographers - have you ever seen one of us jump? Removed downvote, probably a joke :)
12h
comment Burn after read algorythm. Software verification on compromised environment. Software smart card
@mikeazo In short: a method of calculating a checksum without a (practical) possibility for an attacker to alter the memory in such a way that the same checksum is obtained. (yawn)
12h
comment Is it necessary to use single hash function for signature generation and HMAC?
@MattNordhoff fortunately upvotes and downvotes only cancel each other out with regard to the answer, upvotes win from downvotes hands down regarding rep. Of course, if you are like me, that does not mean much, but it should keep you from becoming CodesInChaos :P
12h
revised Security of KDF1 and KDF2 (hash based KDF's)
forgot one mention of KDF0 :(
12h
comment Encryption mode with chained algorithms
Nice, you cannot go much deeper without getting your feet really wet :P
13h
accepted Security of KDF1 and KDF2 (hash based KDF's)
1d
comment Leaving authentication data blank less secure for AES GCM?
Note that the IV does not need to be part of the AAD for GCM mode encryption. It is required for CBC/HMAC schemes, so the inclusion of the IV in the associated data depends on the protocol.
2d
revised Security of KDF1 and KDF2 (hash based KDF's)
Removed mention of KDF0 and KDF1 after I updated my question (now KDF1 and 2)
2d
comment Security of KDF1 and KDF2 (hash based KDF's)
@CodesInChaos Yeah, I figured as much. Otherwise HMAC did not need to have additional passes. But most (if not all) of the time the input is just a key seed or an actual key, so length extensions are generally not applicable, at least not as far as I can see...
2d
revised Security of KDF1 and KDF2 (hash based KDF's)
changed KDF0 to KDF1 and KDF1 to 2, as suggested by answer of Imari
Apr
20
comment Cryptographic library quality
Because it takes a lot of resources away from actually developing the library. They are paper procedures mostly. Furthermore, FIPS and CC (CC much more so) have the nasty side effect that they do not promote updates to libraries.
Apr
19
comment Relation between key size and PRNG state size
Then again, generating a 1024 key in itself is not fine, that key size should no longer be used.
Apr
19
comment Cryptographic library quality
There is no answer here that is not at least opinionated. After the last debacle using a non-managed language (read: one that not intrinsically protects against buffer overflows), I would not consider anything in C. As Botan is object oriented C++ it would come slightly closer. FIPS certification is clearly not enough; it may even be detrimental to perform certification.
Apr
19
comment Security of KDF1 and KDF2 (hash based KDF's)
Hopefully it does not matter if $c$ is signed or unsigned, of course :P. Maybe the security of the KDF can be directly mapped to a hash vs HMAC comparison?
Apr
19
asked Security of KDF1 and KDF2 (hash based KDF's)
Apr
19
comment Questions about Key Derivation Functions
I think you should use HKDF (or a KDF from NIST SP 800-108) if you require a KBKDF (key based KDF) and PBKDF2 if you require a PBKDF (password based KDF) that performs key stretching. You don't need a PBKDF2 (or salt nor iterations) if you already have a key / secret with enough entropy.
Apr
7
answered Convert SpookyHash to semi-secure 192bit hash
Mar
31
comment How can I convert a DER ECDSA signature to ASN.1?
Note that for Java, you can simply perform new BigInteger(1, byte[] r).toByteArray() as the default Java encoding of a BigInteger is identical to the ASN.1 encoding of INTEGER.