用于保持时间戳完整性的校验和

Question

我有基本上是 "ddMMYYHHMMss" 的时间戳。我想做的是每次我运行程序秒值改变但我的校验和保持不变。谁能帮我这个。我希望每次秒（时间）改变时校验和都应该改变。

public class Checksum {
public static void main(String[] args) throws IOException {
    File f = new File("D:/test.txt");
    PrintWriter pw = new PrintWriter(f);
    if(!f.exists()){
        f.createNewFile();
    }
    Date d = new Date();
    SimpleDateFormat sd = new SimpleDateFormat("ddMMYYHHmmss");
    String formatteddate = sd.format(d);
    System.out.println(formatteddate);
    pw.println(formatteddate);
    pw.close();

    BufferedReader br = new BufferedReader(new FileReader(f));
    String line = null;

    while((line = br.readLine()) != null){
        break;
    }
    br.close();

    System.out.println("MD5    : " + toHex(Hash.MD5.checksum(line)));
    System.out.println("SHA1   : " + toHex(Hash.SHA1.checksum(line)));
    System.out.println("SHA256 : " + toHex(Hash.SHA256.checksum(line)));
    System.out.println("SHA512 : " + toHex(Hash.SHA512.checksum(line)));
}
 private static String toHex(byte[] bytes) {
        return DatatypeConverter.printHexBinary(bytes);
    }
}

class CheckSumGenerator {
public enum Hash {

    MD5("MD5"), SHA1("SHA1"), SHA256("SHA-256"), SHA512("SHA-512");

    private String name;

    Hash(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public byte[] checksum(String input) {
        try {
            MessageDigest digest = MessageDigest.getInstance(getName());
            byte[] block = new byte[4096];
            int length;
            if (input.length()> 0) {
                digest.update(block, 0, input.length());
            }
            return digest.digest();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

}

}

Answer 1

您实际上从未将 input 传递到 digest.update(...) 调用中。您总是传递相同的空字节数组：block = new byte[4096]; 因此它总是 return 相同

用于保持时间戳完整性的校验和

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