152,621 reputation
25320519
bio website bolet.org/~pornin
location Quebec City, Canada
age 39
visits member for 3 years, 11 months
seen 49 mins ago

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


9h
comment Is there a protocol for securely trading information between possibly uncooperating agents?
See also security.stackexchange.com/questions/72902/…
14h
comment What are the compatibility implications of generating a new TLS key?
There can be some remaining compatibility issues with RSA-4096; wherever RSA-4096 is supported, RSA-2048 will run too, but the converse is not true. Also, in general, there is no performance issue with RSA in TLS, but a very busy server may still suffer from a 4096-bit modulus, that induces eight times the cost of a 2048-bit modulus. Finally, since we know that existing and foreseeable technology won't break RSA-2048, this raises the question of what exactly you want to achieve with a 4096-bit key...
1d
answered XOR-Cascade of weak hash secure?
1d
answered What are the compatibility implications of generating a new TLS key?
2d
awarded  Guru
Nov
20
awarded  Revival
Nov
19
answered What is preventing us to start using scrypt in production ?
Nov
19
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.
Nov
19
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.