just little sample authentication with bcrypt.

auth.rb

require 'bcrypt'

# if u not ready with bcrypt u can install by typing 'gem install bcrypt' 
accounts = [
  { username: 'choirul', password: 'passwd' },
  { username: 'harpi', password: 'strongpass' },
  { username: 'mahendra', password: 'isverysecret' }
]

def create_hash(string)
  BCrypt::Password.create(string)
end

def verify_hash(string)
  BCrypt::Password.new(string)
end

def create_password(users)
  users.each { |user| user[:password] = create_hash(user[:password]) }
end

def authentication(username, password, users)
  users.each do |u|
    if u[:username] == username && verify_hash(u[:password]) == password
      return users
    end
  end

  'Your username and password is not right'
end

create_password(accounts)
puts authentication('harpi', 'strongspass', accounts)