public void setInitializationVectorSize(int initializationVectorSize) throws IllegalArgumentException {
        if (initializationVectorSize % BITS_PER_BYTE != 0) {
            String msg = "Initialization vector sizes are specified in bits, but must be a multiple of 8 so they " +
                    "can be easily represented as a byte array.";
            throw new IllegalArgumentException(msg);
        }
        this.initializationVectorSize = initializationVectorSize;
    }
Sets the algorithm-specific initialization vector size in bits (not bytes!) to be used when generating
initialization vectors.  The  value must be a multiple of {@code 8} to ensure that the IV can be represented
as a byte array.

@param initializationVectorSize the size in bits (not bytes) of generated initialization vectors.
@throws IllegalArgumentException if the size is not a multiple of {@code 8}.
src/main/java/org/apache/shiro/crypto/cipher/JcaCipherService.java