309 reputation
18
bio website
location Netherlands
age 40
visits member for 3 years, 4 months
seen 22 hours ago

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.


Sep
24
awarded  Autobiographer
Sep
13
awarded  Informed
Aug
29
comment Why should I sign data that's already encrypted?
@Jaap And that's just RSA, for which modular exponentiation is used for both encryption and decryption. It will fail miserably for e.g. Elliptic Curves.
Aug
29
comment Why should I sign data that's already encrypted?
@Jaap Even the PKCS#1 documents, which define the standard way to perform RSA signing or encryption, don't define it as hash then encrypt. It's hash, pad, modular exponentiation. To avoid confusion, they have even given the modular exponentiation a different name (!) for signing and decryption, even though it is the same operation: "RSASP1 and RSAVP1 are the same as RSADP and RSAEP except for the names of their input and output arguments; they are distinguished as they are intended for different purposes" from the RFC
Aug
16
answered Security implication of exporting private key
Aug
3
comment Is Linux really that secure, with only root password denying external access?
@PeterMortensen You are right of course, that's why it is not the perfect place, I'll reword
Aug
3
revised Is Linux really that secure, with only root password denying external access?
added 3 characters in body
Aug
2
answered Is Linux really that secure, with only root password denying external access?
Jul
30
comment Is it possible to distinguish between a SHA256 hash and an ecc256 key?
Could you put the additional question back in? I just answered it.
Jul
30
answered Is it possible to distinguish between a SHA256 hash and an ecc256 key?
Jul
29
comment Is there something similar to pseudorandom generators but in the opposite direction?
Correct. Hash functions can actually be used as a random extractor (see NIST SP 800-90B). NIST however requires that you put in twice as much entropy as the output of the hash function (to call it fully randomized). Of course, if you already have a well seeded CSPRNG you can just take the amount of bytes you require for all practical purposes.
Jul
3
comment Is code-signing with a non-ssl timestamp unsafe?
I guess that as long as you can establish trust (beforehand) for the public key of the time stamp service, and as long as you perform verification, then using a time stamp server over an insecure line is OK.
Jun
30
comment how to rememeber passwords securely?
Cache the result of the PBKDF2 instead?
Jun
24
comment Does SMIME differ from TLS, PGP, DMARC signature, or a Portal Encrypted email message in terms of legal non-repudiation?
Non repudiation in electronic commerce. Does not sound like something that ages quickly.
Jun
23
comment RSA-Based Signature Algorithms
@rapt That's OK, hopefully you do agree on my answer :)
Jun
22
comment openssl - generating rsa key pair - public key
It's at least compatible with X509EncodedKeySpec and the "RSA" KeyFactory in Java. Don't know about others. After PEM decoding, e.g. using Bouncy Castle, of course.
Jun
22
comment RSA-Based Signature Algorithms
@ThomasPornin I feel a bit bad about attacking David though, he's done so much for Bouncy Castle libs :( . It's not personal, just a difference of opinion. Good book otherwise.
Jun
22
awarded  Yearling
Jun
22
answered Java AES encryption output length
Jun
22
comment RSA-Based Signature Algorithms
Note that private key operations may have different security requirements than public key operations. Using one for another may lead to insecurity with regards to side channel attacks (!).