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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.


Mar
12
revised Can the same random number be used in encryption and signing?
added 88 characters in body
Mar
11
answered Can the same random number be used in encryption and signing?
Mar
7
comment Separate keys for encryption and MAC?
@user40602 If you want a low cost / easy to implement KDF you may want to take a look at KDF1/2. For instance you could put the counter on 1 for the encryption key and 2 for the MAC key. For best of breed, take a look at HKDF.
Mar
7
comment FEAL-4 Fk Function 4 Rounds
That link to the spec is pretty useful, but your description of the Fk function seems off.
Mar
7
comment FEAL-4 Fk Function 4 Rounds
Please indicate what you don't understand from the "Key Schedule diagram" in the FEAL specification linked to by Dsthro. It seems pretty clear to me.
Mar
7
revised FEAL-4 Fk Function 4 Rounds
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Mar
7
revised Problem with testing MD5 collisions
added 272 characters in body
Mar
7
revised If a cipher has key length shorter than plaintext, then it is not perfectly secure
added 250 characters in body
Mar
7
comment Problem with testing MD5 collisions
I had 2 bash scripts that had the same hash but printed out something differently. Pretty good practice. Then I archived them and McAfee happily removed the entire backup archive because it thought it had found a virus (instead of just putting the file in the zip archive in quarantine). Thank you McAfee & IT dept...
Mar
7
answered Problem with testing MD5 collisions
Mar
7
comment Problem with testing MD5 collisions
Ah, yes, try this paper, table 2. I've been able to successfully run result for H*, funny enough after reverting the hex values 4 bytes at a time.
Mar
6
answered If a cipher has key length shorter than plaintext, then it is not perfectly secure
Mar
6
comment Is CBC theoretically harder to brute force when compared with ECB?
@laycat No, in case this wasn't clear yet, the comment above isn't an answer - after the edit of the question anyway.
Mar
6
comment Is there a format preserving cryptographically secure hash?
I think it is required to fully state your requirements for this "encryption". Encryption is about confidentiality, a hash is about creating a 1:1 relation with a statically sized value. Maybe you could state them separately below the question?
Mar
6
comment Does the size of a ECDSA key determine the hash algorithm?
I've just now made the question and answer generic so it should now fit the crypto standards here. The question seems reasonable to me and apparently it is considered useful.
Mar
6
revised Does the size of a ECDSA key determine the hash algorithm?
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Mar
6
revised Does the size of a ECDSA key determine the hash algorithm?
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Mar
6
revised Does the size of a ECDSA key determine the hash algorithm?
added 2 characters in body
Mar
5
comment How difficult is it to get a key using simple XOR
@ThomasM.DuBuisson You'll be happy to know that the Sun will not explode, and instead roast us ("us" as in "our atoms") when it becomes a red giant :)
Mar
5
comment How difficult is it to get a key using simple XOR
That should not be a problem as long as the partial keys are generated using a secure PRNG. The chances of the random values being equal are 1 / 2^256, so the same goes for the full key being the same as one of the partial keys (for a setup with 3 parties).