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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.


Dec
3
revised I don't care about replay attacks. What should I do with the nonce in nacl?
added 9 characters in body
Dec
3
answered I don't care about replay attacks. What should I do with the nonce in nacl?
Dec
3
comment Can a secret message be securely transmitted within a MAC tag?
I agree with ushadm that GCM would not be a good idea if the tag size needs to be shortened.
Dec
3
answered Can a secret message be securely transmitted within a MAC tag?
Dec
3
comment Using the same symmetric key in both directions?
If it was, you wouldn't need the additional encryption (but feel free to shoot yourself in the foot).
Dec
2
comment Collision in Merkle–Damgård without a collision in compression function
@CodesInChaos It would be interesting to know what you make of bilge's answer.
Dec
2
revised Collision in Merkle–Damgård without a collision in compression function
edited body
Dec
2
comment Can public key be recovered from chipher text & encrypted private key?
Any progress on this, Dima? Don't forget to follow up on your questions.
Dec
2
revised Verifying DER encoded DSA/ECDSA signature with extra content?
added 101 characters in body
Dec
2
comment Verifying DER encoded DSA/ECDSA signature with extra content?
Sorry, have to agree with thera that there is no explicit standard for handling this, it is up to the protocol. So no clear yes/no answer is possible. Beware that you don't make your verification routines (too) generic; different protocols, different choices. Some duplicate code is OK if the protocols are only identical by chance.
Dec
2
revised Verifying DER encoded DSA/ECDSA signature with extra content?
fleshed it out a bit
Dec
2
answered Verifying DER encoded DSA/ECDSA signature with extra content?
Dec
1
comment Definition of “pepper” in hash functions
I guess that the definition of a pepper is something that you put into a password hash function other than the salt and password. Basically I never heard of option #2, and I'm fully prepared to dismiss this idiotic idea and wipe it from memory again. If you use a "good" PBKDF function (PBKDF2, bcrypt, scrypt) it should already provide a non-random work factor (cost, iteration count), so you don't need a random pepper for that. Casino's may like the odds though :P
Dec
1
comment Rounds in cryptography
SHA-1 is broken in the academic sense as we know that the security provided is lower than the 80 bits expected from the algorithm. As yet, not a single collision has been calculated (but we're getting close). So there is a pretty big gap between broken and exploitable. MD5 does have collisions which you can create in milliseconds, but could still be used in e.g. HMAC without too much fuss (but don't).
Dec
1
revised Rounds in cryptography
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Dec
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comment Rounds in cryptography
In other words, if the attack is of an order too large to be practical, it is only shown to be correct mathematically. If you can make it mathematically likely or provable that you require less operations than brute force to retrieve key / plaintext information then you don't actually need to perform the attack to show a block cipher is broken.
Dec
1
comment suitable programming language for cryptography algorithms
Java also has a byte type, but you cannot specify that it isn't copied to another location or that it is allocated from a specific type of memory (that e.g. isn't copied onto the disk, forgot name of file / partition :) ).
Dec
1
comment suitable programming language for cryptography algorithms
Note that Java 8 seems to extend the key and cipher interfaces to allow purging of sensitive information, but I'm not sure that already takes place.
Dec
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answered suitable programming language for cryptography algorithms
Dec
1
comment Implementing a pseudo random function in practice
Have you tried the NIST defined PRNG's and looked for libraries implementing those?