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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.


13h
comment Is it safe to encrypt random data using ECB mode?
Is there anything against using CBC and a HMAC? Why not default to security?
18h
comment Is only one shared secret generated by ECDH per key pair?
The ideas for ECDH and DH are the same. ECDH has the advantage that it can use the same keys for both ECDH and ECDSA. If ECDH or ECDHE - where the last E is for ephemeral (!) - is used, look at the RFC. I would guess that ECDHE is more common and should be preferred. Note that static-static ECDH can only occur if the client authentication is enabled.
1d
comment What can cause similar MD5 hashes
40 bits of similarity? You could just generate oodles of hashes and order them starting from the least significant bit I suppose. But don't do it on an 8 year old laptop :P
1d
comment Using the Vigenere Cipher to find key
OK, I guess I understand the answer now, thanks for the clarification.
2d
comment Difference between the TLS cipher suites?
Often DH/DSA implementations are also constrained to relatively small key sizes. RSA implementations seem less reluctant to support larger sizes (probably because they are easier to configure - all the parameters are specific to the key and of course because most certificates use RSA).
2d
comment Can Poly1305-AES be used with AES-256?
The question is not just if it can be replaced, the question becomes if it would be any more secure if you do. It seems the polynomial was chosen to provide $2^{106}$ bits of security. Changing the underlying cipher to 256 bits keys may not provide the same level of security increase ("may" means I'm really not sure either way, but it seems to me that it won't).
Mar
28
comment Stacked LFSR - why not used?
I think LFSR's are primarily used on constrained environments, so requiring a very large state (and at least 1.25 times the processing power) is quite a big thing to ask.
Mar
28
comment Assemble RSA keys from components
I've got the strong feeling that this is still at the wrong place. It should include runtime etc. and be asked at StackOverflow.
Mar
27
comment How efficient is the error correcting code?
Comes to that, what do you mean with efficient? Efficient compared to order, CPU time, output size, cryptographic strength, size of the acronym?
Mar
27
comment Collision attacks on digital signatures
See section 5.3: Constructing colliding certificates of "MD5 considered harmful today - Creating a rogue CA certificate"
Mar
27
comment Key sizes supported by 3DES
I guess I can agree on that. The keys should be indistinguishable from random for ciphers, so as long as that pre-condition is taken into account DES AAA is not triple DES. To be completely fair a check should be really present to check that situation though, otherwise the name of the algorithm would depend on the input, which is kind of weird. Or we could just stop using the frickin' 3DES algorithm of course ;)
Mar
27
comment Using the Vigenere Cipher to find key
The second part of your description reads like a method of breaking a one time pad (what sub-keys are you referring to?).
Mar
27
comment Key sizes supported by 3DES
Do you have a reference to a product that specifies 256 bit triple DES? It's nice to have a good laugh from time to time :)
Mar
27
comment Key sizes supported by 3DES
If I remember correctly the idea that 3DES would emulate DES when used with a single 64 bit key for key 1, 2 and 3 (or key A, B and C if I remember the specs correctly) was meant as specific property of 3DES as you could use the same circuitry to accomplish both.
Mar
27
comment Practical brute-force attack on 128 bit encryption
Because KeySpace/2 is the average amount of tries required?
Mar
27
comment Practical brute-force attack on 128 bit encryption
Amended answer, including a pointer to the 72 bit key space search.
Mar
26
comment Encode-decode with different block sizes?
You're welcome to post this on StackOverflow, but in that case please include the source code (as a self contained example).
Mar
26
comment Can machine learning analyze random number generator?
It's good background info, I'm not sure if it qualifies as an answer. AES-CTR is close but not quite a CSPRNG I guess, it does not offer re-seed possibilities for instance.
Mar
26
comment Can machine learning analyze random number generator?
I'm pretty sure those tests are not considered "machine learning".
Mar
26
comment AES or Serpent-Twofish-AES
No it shouldn't.