5,480 reputation
2734
bio website
location Netherlands
age 40
visits member for 2 years, 11 months
seen 10 hours ago

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.

On crypto I mainly answer less mathematically inclined questions, leaving security proofs to the theoretical cryptographers and analysts.


Nov
18
comment Find the encryption method from the cipher and plaintext
I think we are not going to loose sleep over this, MinusSomething, deciphering ciphertext is explicitly off topic here.
Nov
18
comment Bouncy jdk 1.51 Serpent KAT tests vs Nessie vectors
If we would just all keep to big endian with most significant bit at the left, counting from 0 to 7 for bits everything would become so much easier. Little endian is only interesting for Intel and then only for the machine word size. I don't think the performance benefits come even close to outweighing the stupidity of little endian. Lets reverse the bytes not the bits. Right.
Nov
18
comment Bouncy jdk 1.51 Serpent KAT tests vs Nessie vectors
@John I couldn't find any other test vectors either, but I guess it is solved now...
Nov
18
comment Bouncy jdk 1.51 Serpent KAT tests vs Nessie vectors
Send a mail to one of the BC maintainers...
Nov
18
comment Bouncy jdk 1.51 Serpent KAT tests vs Nessie vectors
Serpent-0 and Serpent-1?
Nov
17
revised what does rsaSha512Sign do?
added 505 characters in body
Nov
17
comment what does rsaSha512Sign do?
The dev team not being available for such a simple question and not documenting properly. Nice team.
Nov
17
answered what does rsaSha512Sign do?
Nov
17
comment How can I calculate the size of an encryption key?
Note that there are differences between the size and strength of a key. Now if the values are randomly chosen in a specific range, then the size of the ranges added up are considered the key size (given that the values are independent of each other and both count towards the security). The key strength obviously depends on the algorithm. Often the effective key strength is the complexity of finding the key given the least complex method and the key size.
Nov
17
comment Many single-time use keys encryption scheme (not Shamir's Shared Secret)
Please indicate why a particular solution is not valid.
Nov
17
comment RSA with PKCS#7 and DES-EDE3-CBC (and padding)
@dave_thompson_085 In that case it might also be that somebody tried to encrypt with the private key; I am not sure what happens if somebody tried to do that in OpenSSL. I've seen software "magically" change the padding method.
Nov
16
comment RSA with PKCS#7 and DES-EDE3-CBC (and padding)
You are mixing up PKCS#7 padding for symmetric ciphers with PKCS#1 v1.5 padding for RSA signature generation. PKCS#7 is a standard for the cryptographic message syntax (CMS). PKCS#7 padding for symmetric ciphers is only a tiny part of it (about a single line for the definition).
Nov
16
comment OpenSSL RSA same plaintext but different ciphertext
In general, identical plaintext should result in a different ciphertext. Otherwise you leak information to an attacker. If the attacker can guess what a specific ciphertext means he knows that a repetition of the ciphertext means the same thing. This goes for symmetric ciphers (the use of an IV or nonce) as well as asymmetric ones (random padding).
Nov
16
comment OpenSSL RSA same plaintext but different ciphertext
Also note my explicit question about the attacks on textbook RSA.
Nov
16
revised OpenSSL RSA same plaintext but different ciphertext
deleted 22 characters in body; edited title
Nov
15
comment Why we can't implement AES 512 key size?
From the Rijndael proposal: "For Rijndael, the block length and the key length can be independently specified to any multiple of 32 bits, with a minimum of 128 bits, and a maximum of 256 bits"
Nov
15
comment Why we can't implement AES 512 key size?
It looks suspiciously like one of the earlier snake oil papers...same organization. Buy me a paper?
Nov
14
comment How to perform frequency analysis of a substitution cipher using a Base64 alphabet
If the input is text then looking for the distribution of the higher 0 bits of the ASCII encoding would give great opportunities as well.
Nov
14
revised How to perform frequency analysis of a substitution cipher using a Base64 alphabet
edited title
Nov
14
comment How can CBC-MAC be secure when message length is fixed?
I put the mathematical parts in mathematical notation, but I think you're missing some parentheses in your 4th paragraph, the XOR must be over an equal sized value. Could you have a look?