Coverity found possible division by zero code.

https://scan7.coverity.com/reports.htm#v23632/p11778/fileInstanceId=12563831&defectInstanceId=2991543&mergedDefectId=1422738

        private byte[] pkcs7Pad(byte[] buffer, int blockSize) {
            int len = buffer.length;
            int toFill = blockSize - (len % blockSize);
            byte[] padded = Arrays.copyOf(buffer, toFill + len);
            Arrays.fill(padded, len, padded.length, (byte) toFill);
            return padded;
        }

blockSize could be 0 as encrypt.getBlockSize() return 0 if used algorithm is not blocked-based. Although default cyptographic algoritm is block-based DEFAULT_CRYPTOGRAPHIC_ALGORITHM = "AES/CBC/NoPadding" , this is configurable with cryptoAlg option and thus non-block-based algorithm can be configured.