crypto.rb

java_import 'java.security.MessageDigest'
java_import 'java.util.Base64'

def hash256(input)
  md = MessageDigest::getInstance('SHA-256')
  md.digest(md.digest(input.to_java_bytes))
end

def hash160(input)
  md = MessageDigest::getInstance('SHA-256')
  sha1 = MessageDigest::getInstance('SHA-1')
  sha1.digest(md.digest(input.to_java_bytes))
end

puts Base64::getEncoder().encodeToString(hash256(''))  # --> Xfbg4nYTWdMKgnUFjimfzAOBU0VF9Vz0PkGYP11MlFY=
puts Base64::getEncoder().encodeToString(hash160(''))  # --> 0o6Kvb13ekgs4O5cJIFKyuUqq/4=


md = MessageDigest::getInstance('SHA-256')

h = md.digest(''.to_java_bytes)
size = h.length

hash_hash = h + h

java.lang.System::arraycopy(h, 0, hash_hash, 0, size)
java.lang.System::arraycopy(h, 0, hash_hash, size, size)

puts Base64::getEncoder().encodeToString(md.digest(hash_hash))

md.reset()

md.update(h)
md.update(h)

puts Base64::getEncoder().encodeToString(md.digest())