Byzantine Failures
Readings - Practical Byzantine Fault Tolerance.pdf Byzantine PAXOS.pdf Notes What can be potential byzantine failures? Wrong replies which cannot be detected Halt consensus(same as crash so not really byzantine) Internal state mismanagement(same as crash) Forgery(Use public/private keys to encrypt data) Converting paxos to byzantine paxos Strategy 1(Outvoting) Increase the number of servers and increase quorum requirement to N = 3f + 1, Q = 2f + 1 Normal paxos wouldn’t work where let’s say- Thought process of increasing servers: There are 4 servers. S1, S2, S3 are normal servers and S4 is a malicious one. Let’s say S1 prepares and accepts a value with itself S1, S3 and S4. v1 is decided for number 1. S1 goes down and S2 comes up. S2 tries to prepare a new number and receives 1,v1 from S3 but 2,v2 from S4. How do you decide which is the correct value? We outvote it meaning we’ll have to increase number of good servers. ...