public static BigDecimal vigenere(BigDecimal bd, String key, int mode) {
                if (bd == null || key == null)
                        return null;
                if (mode == MyTools.ENCRYPT_MODE) // 加密
                {
                        String str = bd.toPlainString();
                        byte[] strBytes = str.getBytes();
                        byte[] keyBytes = key.getBytes();
                        int keyLength = keyBytes.length;
                        byte[] result = new byte[strBytes.length];
                        for (int i = 0; i < strBytes.length; i++) {
                                if (strBytes[i] == 43 || strBytes[i] == 45 || strBytes[i] == 46)// 正負(fù)號(hào)和小數(shù)點(diǎn)不處理
                                {
                                        result[i] = strBytes[i];
                                        continue;
                                }
                                result[i] = (byte) ((strBytes[i] - 48 + keyBytes[i % keyLength] - 48) % 10 + 48);
                        }
                        String inDateBase = new String(result);
                        if (!str.substring(0, 1).equals("-") && !str.substring(0, 1).equals("+"))
                                inDateBase = "1" + inDateBase;
                        else if (str.substring(0, 1).equals("-") || str.substring(0, 1).equals("+"))
                                inDateBase = inDateBase.substring(0, 1) + "1" + inDateBase.substring(1);
                        return new BigDecimal(inDateBase);
                } else if (mode == MyTools.DECRYPT_MODE) { // 解密
                        String str = bd.toPlainString();
                        if (!str.substring(0, 1).equals("-") && !str.substring(0, 1).equals("+"))
                                str = str.substring(1);
                        else if (str.substring(0, 1).equals("-") || str.substring(0, 1).equals("+"))
                                str = str.substring(0, 1) + str.substring(2);
                        byte[] strBytes = str.getBytes();
                        byte[] keyBytes = key.getBytes();
                        int keyLength = keyBytes.length;
                        byte[] result = new byte[strBytes.length];
                        for (int i = 0; i < strBytes.length; i++) {
                                if (strBytes[i] == 43 || strBytes[i] == 45 || strBytes[i] == 46)// 正負(fù)號(hào)和小數(shù)點(diǎn)不處理
                                {
                                        result[i] = strBytes[i];
                                        continue;
                                }
                                int temp = strBytes[i] - keyBytes[i % keyLength];
                                if (temp < 0)
                                        temp += 10;
                                result[i] = (byte) (temp % 10 + 48);
                        }
                        return new BigDecimal(new String(result));
                }
                return null;
        }