merkle.rb

require "sequel"
require "merkle-hash-tree"
require "rbnacl"
require "digest"

DB = Sequel.connect('postgres://postgres@192.168.33.10/merk')
def build_chain(head)
    chain = DB.from(:chains)[head: head]
    if chain[:previous_head] == "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
        [chain[:body]]
    else
        build_chain(chain[:previous_head]) << chain[:body]
    end
end

head = "529da179869b61355f106f22074b7be466d2f2335ebb464f7e71b360cd62fc40"
mht_head = RbNaCl::Util.bin2hex(MerkleHashTree.new(build_chain(head), Digest::SHA256).head)
p head == mht_head