UDP for games – encryption and DDoS protection

Post by hefty » Thu, Apr 28, 2016, 3:06 PM UTC

dividuum wrote: post #34

chmike wrote: post #32

Earlier quoted context omitted.

Sorry, my age may be lower than five. I don't understand. You explain that a hash is computed over a string that is the concatenation of a server key, a random number and a client adjusted nonce. you then lost me with the four bytes. I thought that we were talking about a string of chars, not an array of bytes. The nonce is an integer value ? The client then increases the nonce value I guess. But how does the client…

The basic idea is: The client has to create a hash that satisfies a certain condition: Like the first n-digits must be 0, or maybe "the last bytes (when interpreted as a single 32 number) must be larger than x". So the client does this: from itertools import count import hashlib for i in count(): h = hashlib.md5("some-nonce:%d" % i).hexdigest() if h.startswith("000000"): print i break The value "some-nonce" is provid…

Post by grenoire » Thu, Apr 28, 2016, 4:12 PM UTC

hefty wrote: post #41

dividuum wrote: post #34

Earlier quoted context omitted.

The basic idea is: The client has to create a hash that satisfies a certain condition: Like the first n-digits must be 0, or maybe "the last bytes (when interpreted as a single 32 number) must be larger than x". So the client does this: from itertools import count import hashlib for i in count(): h = hashlib.md5("some-nonce:%d" % i).hexdigest() if h.startswith("000000"): print i break The value "some-nonce" is provid…

Maybe I'm taking your example a bit far, but it seems like you'd have to choose the hashing function carefully, correct? To use your example, it must be 100% certain that a hash with 6 leading zeros is possible to generate with md5. Also, I'm assuming you don't want clients spending too long on the problem, so it seems like you'd want to have a prediction of roughly how long it would take to compute the answer. Other…

Post by zamalek » Thu, Apr 28, 2016, 5:16 PM UTC

_qbjt wrote: post #42

zamalek wrote: post #29

Earlier quoted context omitted.

TCP and UDP occurring over the same route on a WAN can wreak havoc with UDP packet loss.[1] Using both is only a good idea up until you dig deep into socket performance. A network is not a piece of software where you can isolate things and expect them to behave in an isolated way, everything you push over it interacts with everything else that you are pushing over it. This "use UDP and TCP" is a dangerous anti-patter…

With my example for login, my assumption was that one would use short-lived TCP connections (i.e. server receives login packet, sends success/fail and finally closes the connection), not a simultaneous, persistent connection where TCP congestion (and thus UDP packet loss) becomes an issue. But maybe I'm wrong on this one. Thanks for sharing by the way, great article (although as an aside, some of those graphs are rea…

Post by chmike » Fri, Apr 29, 2016, 3:48 AM UTC

dividuum wrote: post #34

chmike wrote: post #32

Earlier quoted context omitted.

Sorry, my age may be lower than five. I don't understand. You explain that a hash is computed over a string that is the concatenation of a server key, a random number and a client adjusted nonce. you then lost me with the four bytes. I thought that we were talking about a string of chars, not an array of bytes. The nonce is an integer value ? The client then increases the nonce value I guess. But how does the client…

The basic idea is: The client has to create a hash that satisfies a certain condition: Like the first n-digits must be 0, or maybe "the last bytes (when interpreted as a single 32 number) must be larger than x". So the client does this: from itertools import count import hashlib for i in count(): h = hashlib.md5("some-nonce:%d" % i).hexdigest() if h.startswith("000000"): print i break The value "some-nonce" is provid…