在Java中通过SHA-256哈希字符串

Question

通过环顾四周和一般的互联网,我找到了Bouncy Castle.我想使用Bouncy Castle(或其他一些免费提供的实用程序)在Java中生成一个SHA-256 Hash of String.看看他们的文档,我似乎找不到任何我想做的好例子.这里有人可以帮帮我吗？

Answer 1

要散列字符串,请使用内置的MessageDigest类:

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.nio.charset.StandardCharsets;
import java.math.BigInteger;

public class CryptoHash {
  public static void main(String[] args) throws NoSuchAlgorithmException {
    MessageDigest md = MessageDigest.getInstance("SHA-256");
    String text = "Text to hash, cryptographically.";

    // Change this to UTF-16 if needed
    md.update(text.getBytes(StandardCharsets.UTF_8));
    byte[] digest = md.digest();

    String hex = String.format("%064x", new BigInteger(1, digest));
    System.out.println(hex);
  }
}

在上面的代码段中,digest包含散列字符串并hex包含一个带有左零填充的十六进制ASCII字符串.

Answer 2

这已经在运行时库中实现.

public static String calc(InputStream is) {
    String output;
    int read;
    byte[] buffer = new byte[8192];

    try {
        MessageDigest digest = MessageDigest.getInstance("SHA-256");
        while ((read = is.read(buffer)) > 0) {
            digest.update(buffer, 0, read);
        }
        byte[] hash = digest.digest();
        BigInteger bigInt = new BigInteger(1, hash);
        output = bigInt.toString(16);
        while ( output.length() < 32 ) {
            output = "0"+output;
        }
    } 
    catch (Exception e) {
        e.printStackTrace(System.err);
        return null;
    }

    return output;
}

在JEE6 +环境中,还可以使用JAXB DataTypeConverter:

import javax.xml.bind.DatatypeConverter;

String hash = DatatypeConverter.printHexBinary( 
           MessageDigest.getInstance("MD5").digest("SOMESTRING".getBytes("UTF-8")));

Answer 3

您不一定需要BouncyCastle库.以下代码显示了如何使用Integer.toHexString函数执行此操作

public static String sha256(String base) {
    try{
        MessageDigest digest = MessageDigest.getInstance("SHA-256");
        byte[] hash = digest.digest(base.getBytes("UTF-8"));
        StringBuffer hexString = new StringBuffer();

        for (int i = 0; i < hash.length; i++) {
            String hex = Integer.toHexString(0xff & hash[i]);
            if(hex.length() == 1) hexString.append('0');
            hexString.append(hex);
        }

        return hexString.toString();
    } catch(Exception ex){
       throw new RuntimeException(ex);
    }
}

特别感谢来自这篇文章的user1452273:如何在Java中使用sha256散列一些字符串？

保持良好的工作 !

Answer 4

在任何jce提供程序中使用哈希码时,首先尝试获取算法的实例,然后使用要哈希的数据更新它,并在完成后调用摘要以获取哈希值.

MessageDigest sha = MessageDigest.getInstance("SHA-256");
sha.update(in.getBytes());
byte[] digest = sha.digest();

您可以根据需要使用摘要获取base64或hex编码版本

Answer 5

Java 8:Base64可用:

    MessageDigest md = MessageDigest.getInstance( "SHA-512" );
    md.update( inbytes );
    byte[] aMessageDigest = md.digest();

    String outEncoded = Base64.getEncoder().encodeToString( aMessageDigest );
    return( outEncoded );

Answer 6

我想你使用的是没有SHA-256的相对旧的Java版本.因此,您必须将BouncyCastle Provider添加到Java版本中已提供的"安全提供程序"中.

    // NEEDED if you are using a Java version without SHA-256    
    Security.addProvider(new BouncyCastleProvider());

    // then go as usual 
    MessageDigest md = MessageDigest.getInstance("SHA-256");
    String text = "my string...";
    md.update(text.getBytes("UTF-8")); // or UTF-16 if needed
    byte[] digest = md.digest();