Returns a basic n-bit checksum of the characters in self; the checksum is the sum of the binary value of each byte in self, modulo 2**n - 1:
'hello'.sum # => 532 'hello'.sum(4) # => 4 'hello'.sum(64) # => 532 'тест'.sum # => 1405 'こんにちは'.sum # => 2582
This is not a particularly strong checksum.