What is sha 256

sha256.rb

require 'digest'

database = ['123456', 'monkey', '1ljflkdjsiolk', 'abcdefghijk']

def sha256(digest)
	Digest::SHA256.hexdigest(digest)
end

puts "unencrypted passwords"
puts database

encrypted_passwords = database.map{|pw| sha256(pw << "salt")}

puts "encrypted_passwords"
puts encrypted_passwords

passwords = [
'123456',
'123456789',
'qwerty',
'12345678',
'111111',
'1234567890',
'1234567',
'password',
'123123',
'987654321',
'qwertyuiop',
'mynoob',
'123321',
'666666',
'18atcskd2w',
'7777777',
'1q2w3e4r',
'654321',
'555555',
'3rjs1la7qe',
'google',
'1q2w3e4r5t',
'123qwe',
'zxcvbnm',
'1q2w3e',
]

rainbow_table = {}
passwords.map{|pw| rainbow_table[sha256(pw)] = pw}

puts "rainbow_table"
puts rainbow_table

puts "The encrypted password is: "
puts rainbow_table[encrypted_passwords[0]]