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Security professional with many years of experience with the practical application of cryptographic algorithms and protocols. I'm helping with the design of protocols and API's within international standardization bodies. Lead developer of a common criteria certified product. Over 30 years of general experience with computers.

Currently looking for a new position in the Netherlands.


Nov
26
comment Maximum length in bits of the product n=pq
Partial answer at best, there were two related questions.
Nov
26
comment Repeatedly using same key on different plaintexts
I've added an answer that directly addresses the question (about the key). If you don't mind I've not included the attacks on the modes of operation, those are sufficiently covered by the answers of John Meacham & DuneWalker.
Nov
26
answered Repeatedly using same key on different plaintexts
Nov
26
comment CoAP authentication using DTLS
Yep, that's it.
Nov
25
revised CoAP authentication using DTLS
edited title
Nov
25
comment CoAP authentication using DTLS
Tried to explain, but without information on what precisely you don't get, it is impossible to create a better answer.
Nov
25
comment CoAP authentication using DTLS
(including grammar mistake, I mean, "Both $K_i$ and ${nonce}_1$ are 128 bit each")
Nov
25
answered CoAP authentication using DTLS
Nov
25
comment Are there any digital signature algorithms in common use that result in 32-byte signatures?
... relatively well known by cryptographers, it's not like you see many Schnorr signatures in the wild (yet).
Nov
25
comment Less known hash functions producing 128 bit hash
Those constant tables may be your best bet, you could compare them with existing tables. Trying to establish the exact input and trying everything known is another.
Nov
24
comment Less known hash functions producing 128 bit hash
@fasmotol If no cutting is involved you should know more. How don't you have any info on the algorithm and still know no cutting is involved? Are you sure you know all the bits of the input?
Nov
24
comment Real life RSA/El Gamal examples
Well, you can always go for some NIST test vectors...
Nov
24
comment Compact digital signature for noisy data
@fgrieu Reed-Solomon is however also used for PAR2 where entire packets can be missing (I think grouping the bits differently for the ECC - i.e. over the first bits of all symbols etc - does the trick)...
Nov
23
comment Why we can't implement AES 512 key size?
Is there some kind of authority where we should report this obvious abuse? If there is something I really hate it is fake scientific papers and results.
Nov
21
revised Hash collision using the leading 40-bits of SHA-1
added 92 characters in body; edited title
Nov
21
comment Hash collision using the leading 40-bits of SHA-1
@user1813580 A quick test confirms this.
Nov
21
comment Hash collision using the leading 40-bits of SHA-1
will find a collision -> won't find a collision?
Nov
21
comment Encryption of big files in Java with AES/GCM
@alejo I started to doubt myself and have looked up the requirements from NIST SP 800-38D and changed my answer accordingly. If unsure, look up the standard document.
Nov
21
revised Encryption of big files in Java with AES/GCM
deleted 97 characters in body
Nov
20
comment AES - Encrypting multiple blocks of files
If you prefix something it becomes larger? If the maximum size of the encrypted blocks can be somewhat larger than the plaintext you can just use CBC + padding or CTR and prefix the IV.