encrypt abstract method
inp: the total bytes in plain textinpOff: the byte offset to start encryption atinpLength: the number of bytes (length) to encryptout: the buffer to write the encrypted output inoutOff: the byte offset to write the encrypted output to
returns the length of the new encrypted output
Implementation
FutureOr<int> encrypt(
Uint8List inp, int inpOff, int inpLength, Uint8List out, int outOff);