MD5 (non primitive and with primitive) is broken because it relies on the conversion of Character to SmallInteger so the method shiftBits: Problem happens at ThirthyTwoBitRegister>>reverseLoadFrom:at: which is called from MD5NonPrimitive>>proccessBuffer: Error is: Instance of Character did not understand #bitShift and happened at: reverseLoadFrom: aByteArray at: index "Load my 32-bit value from the four bytes of the given ByteArray starting at the given index. Consider the first byte to contain the most significant bits of the word (i.e., use big-endian byte ordering)." hi := ((aByteArray at: index + 3) bitShift: 8) + ( aByteArray at: index + 2). low := ((aByteArray at: index + 1) bitShift: 8) + ( aByteArray at: index). -- The information contained in this message is confidential and intended to the recipients specified in the headers. If you received this message by error, notify the sender immediately. The unauthorized use, disclosure, copy or alteration of this message are strictly forbidden and subjected to civil and criminal sanctions.