152,486 reputation
25319519
bio website bolet.org/~pornin
location Quebec City, Canada
age 39
visits member for 3 years, 11 months
seen 1 hour ago

Cryptographer, programmer in several languages (C, Java, several assemblies, Pascal, Forth...). I also have a life.


2d
awarded  Revival
2d
answered What is preventing us to start using scrypt in production ?
2d
comment What's the difference between X.509 and PKCS#7 Certificate?
It may be worth mentioning that a PKCS#7/CMS SignedData structure used as a mere bag for certificates is unordered: you can put several certificates, but the format does not keep track of any ordering. Therefore, it can transport a certificate chain exactly as well as IKEA sells furniture. Decoders must still work out who signed who in the chain.
2d
comment Is return oriented programming applicable to pure Java code?
ROP is useful when you found a vulnerability that allows redirecting execution to an arbitrary point (e.g. a buffer overflow on the stack, that allows overwriting the "return address" slot), but then countermeasures such as ASLR and DEP prevent you from simply pushing your payload code as data and jumping into it. All of ROP is about reusing the existing code (from the application itself and its libraries) as "payload".
Nov
19
answered Is return oriented programming applicable to pure Java code?
Nov
19
comment Get the Signature algorithm from a public key?
The details of the signature algorithm are not in the certificate. The certificate contains only the public key (so: "RSA"), not any information on any algorithm with which that key has been used.
Nov
19
awarded  key-exchange
Nov
18
answered Get the Signature algorithm from a public key?
Nov
18
answered Authenticated Diffie Hellman Key Exchange
Nov
18
awarded  Necromancer
Nov
16
comment TLS library problem when connecting to Dovecot
Chances are that you concatenated the certificates in the wrong order. Postfix will use the first certificate in the file as its own certificate, and will try to match the private key with the public key in that certificate.
Nov
16
answered TLS library problem when connecting to Dovecot
Nov
15
awarded  Guru
Nov
14
answered Are Java applications vulnerable to CVE-2014-6321 (WinShock)?
Nov
14
comment Is TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256 a safe cipher suite to use?
Some people may also argue that efficient GCM implementations that do not use the AES-NI opcodes must use large tables, that make them somewhat vulnerable to side-channel attacks based on cache misses.
Nov
14
comment Is TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256 a safe cipher suite to use?
@CodesInChaos: well, from a theoretical point of view, GCM is better because it leaves much less room for implementers to goof it up. Concluding that they did not goof up is some kind of a stretch, though.
Nov
14
comment What's the difference between VPN over TCP vs UDP?
TCP provides a bidirectional tunnel for data, but relies on packets, so there will be some "administrative" packets, e.g. acknowledges: this is the TCP overhead. For instance, if machine A sends 10 MB to machine B, machine B will also send some packets to A confirming reception. When you do a VPN over TCP, the VPN has its own TCP-based overhead, and transports the administrative packets for any connection within the VPN -- this is the "pay twice" thing.
Nov
14
answered Is TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256 a safe cipher suite to use?
Nov
13
awarded  Enlightened
Nov
13
answered Viruses From Email Attachments