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location Netherlands
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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.


Aug
19
comment Entropy Loss of KDFs
Well, it was "for example" :P Besides the pun, lets not specialize answers too much. Thanks for the edit, had already voted up...
Aug
19
comment How to generate ECC (160 bits) Keys with OpenSSL?
Is there a close, RTFM?
Aug
19
answered Cryptography vs Security
Aug
19
comment Entropy Loss of KDFs
Good answer, but I guess you also need to state that if you provide more than 128 bits of entropy that the entropy loss will be the difference between 128 and the amount of entropy (+ possibly part of a single bit?).
Aug
19
comment GPG & Mcrypt - difference?
Note that the mcrypt C library has had little maintenance over the years although apparently the developers are planning a new release.
Aug
18
answered GPG & Mcrypt - difference?
Aug
18
comment How dead is braid based cryptography
I can understand the close votes here (primarily opinion based). As long as there is no proof that a specific method will not provide security then it is hard to say for an entire class of problems that they are not suitable for cryptography. On the other hand, I know at least one person (yourself) that somebody is taking an interest, so it's not completely dead in that sense.
Aug
18
comment Session-specific Symmetric Key Derivation Using SHA256
Closely related: crypto.stackexchange.com/questions/15673/…
Aug
18
comment Keep GPG revocation certificate in safe place?
This sounds more like a question for security.stackexchange.com, it seems to only scratch the surface of cryptography.
Aug
18
comment How can finding a collision help an attacker with tampering messages with HMAC
For MAC, not even that, as you need to find a message that creates a collision when combined with the key. So a collision is not very likely or useful. But because the key should be at least as large as the output size, any effective attacks (i.e. better than brute force) on the HMAC should have less complexity by definition than an attack on the key.
Aug
17
comment public key delivery without third party
Yes, it is (vulnerable to MitM attacks), unless some kind of PKI is in place to verify the public keys. See Otus comment on Web of Trust to see how e.g. PGP handles this.
Aug
17
comment How can I fix a corrupted PGP file?
You're one lucky guy :). If you can program, you could just create a program using Bouncy Castle libraries trying to parse the PGP format while stripping off an X number of bytes in repetition. If the parsing succeeds, you print the offset and/or continue with decryption. No doubt you can do the same thing with scripting and PGP command line.
Aug
17
revised How can I fix a corrupted PGP file?
deleted 18 characters in body
Aug
17
comment How can I fix a corrupted PGP file?
Did you just prefix them, mix them in or even XOR or replace the bytes in the header? Please add any relevant information that you can think of.
Aug
17
comment Is my id obfuscation algorithm secure?
Usually keys on smart cards are actually better protected than data, so storing ID's instead of keys does not seem to be such a good idea. Using a higher end CC certified chip with asymmetric crypto (ECDH) seems to be a good idea to start off with.
Aug
16
comment Advantages of 64-bit CPU smartphone
I'm not sure about the correctness of the last statement. Normally a user should not have to enter a key directly, let alone a smartphone user.
Aug
16
revised Advantages of 64-bit CPU smartphone
added 18 characters in body
Aug
16
answered public key delivery without third party
Aug
16
revised Multi-key decryption
added 1 character in body
Aug
16
comment Using multiple secret keys
For others: if you just want to combine keys with sufficient entropy, use a KBKDF (such as HKDF), if these keys together contain slightly too little entropy use a PBKDF (such as PBKDF2) with a high iteration count. If you have too little entropy for either scheme, you're scr\b\b\b out of options.