README.md

PoS-visualization

A textual visualization of Proof-of-Stake (PoS) blockchains.

We present an adversarial strategy which attacks the consistency property of PoS blockchain protocols under the longest-chain rule in the eventual consensus paradigm, such as Ouroboros, Ouroboros Praos, and Snow White. This adversarial strategy is described and analyzed in https://eprint.iacr.org/2017/241.pdf.

Background

Rounds in a blockchain protocol execution can be labeled as either adversarial or honest. Thus we can think of a blockchain execution of n rounds on an n-bit Boolean string w; this string is called a characteristic string.

In a Proof-of-Stake blockchain execution, an honest round can yield a single block whereas an adversarial round can yield zero, one, or more blocks. Each block builds upon a previous block; hence the entire execution looks like a rooted tree. This tree is called the fork and each root-to-leaf path (i.e., each blockchain) is called a tine. A tine is honest if it ends at a block generated at an honest round; otherwise, it is adversarial. A tine is competitive if it is at least as long as the longest honest tine. The honest tines follow the longest-chain rule, i.e., they always build on a competitive tine.

In this repository, we build an adversarial strategy which attacks the consistency property of the blockchain protocol. That is, it creates forks with competitive tines that diverge long ago. This adversarial strategy is described and analyzed in https://eprint.iacr.org/2017/241.pdf.

Example code

Please refer to test.py for detailed examples.

$ ./optfork.py -w 1101100110110110 -a branching
Using adv: branching
Using w: 1101100110110110 n: 16

===== Fork on w = 1101100110110110 (16 bits) =====
----Tines (3)----
tine (*)------(3)------(6)(7)
tine (*)------(3)------(6)---[8]---(10)
tine (*)------(3)------(6)---[8][9]------------(13)--------(16)

Here, the node (*) is the root node and it is considered honest. The 0-bits in w correspond to honest rounds; the 1-bits correspond to adversarial rounds. There are three tines (i.e., blockchains) in the execution of this adverary. In each tine, blocks from an honest round h are marked as (h) and the blocks from an adversarial round a are marked as [a].

Below is the full specification of the file optfork.py.

$ ./optfork.py --help

Options:
  -h, --help            show this help message and exit
  -a ADV, --adversary=ADV
                        adversary type, one of ['opt', 'branching',
                        'revealing', 'toofluffy']
  -w W, --w=W           characteristic string, should end with a 0
  -r, --random          use a random string of N bits
  -n N, --n=N           use a random string of N bits
  -x D, --max-delete-blocks=D
                        delete X blocks from the end of non-longest tines
  -p SPLIT_PROB, --split-prob=SPLIT_PROB
                        splitting probability
  -d, --diagnostics     show diagnostics
  -s, --stats           show stats
  -m, --matrix          show matrix
  -t, --tines           show tines
  -v, --verbose         verbose
  -e, --diag-verbose    verbose
  -l, --double          verbose
  -b BREAK_TIE, --break-tie=BREAK_TIE
                        tie-breaking basis, one of [None, 'slot', 'reach']