Java Tutorial/Security/SHA1 Secure Hash Algorithm

Basic IO example using SHA1

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.security.DigestInputStream;
import java.security.DigestOutputStream;
import java.security.MessageDigest;
public class MainClass {
  public static void main(String[] args) throws Exception {
    byte[] input = "1234567".getBytes();
    MessageDigest hash = MessageDigest.getInstance("SHA1");
    ByteArrayInputStream bIn = new ByteArrayInputStream(input);
    DigestInputStream dIn = new DigestInputStream(bIn, hash);
    ByteArrayOutputStream bOut = new ByteArrayOutputStream();
    int ch;
    while ((ch = dIn.read()) >= 0) {
      bOut.write(ch);
    }
    byte[] newInput = bOut.toByteArray();
    System.out.println("in digest : " + new String(dIn.getMessageDigest().digest()));
    DigestOutputStream dOut = new DigestOutputStream( new ByteArrayOutputStream(), hash);
    dOut.write(newInput);
    dOut.close();
    System.out.println("out digest: " + new String(dOut.getMessageDigest().digest()));
  }
}

Encrypt a password

public class Main {
  public static void main(String arg[]) throws Exception {
    System.out.println(encrypt("String"));
  }
  public static byte[] encrypt(String x) throws Exception {
    java.security.MessageDigest d = null;
    d = java.security.MessageDigest.getInstance("SHA-1");
    d.reset();
    d.update(x.getBytes());
    return d.digest();
  }
}

PSS parameter recovery and encoding

import java.security.AlgorithmParameters;
import java.security.Security;
import java.security.Signature;
import java.security.spec.PSSParameterSpec;
import org.bouncycastle.asn1.ASN1InputStream;
import org.bouncycastle.asn1.util.ASN1Dump;
public class MainClass {
  public static void main(String[] args) throws Exception {
    Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());
    Signature signature = Signature.getInstance("SHA1withRSAandMGF1", "BC");
    signature.setParameter(PSSParameterSpec.DEFAULT);
    AlgorithmParameters params = signature.getParameters();
    ASN1InputStream aIn = new ASN1InputStream(params.getEncoded("ASN.1"));
    System.out.println(ASN1Dump.dumpAsString(aIn.readObject()));
  }
}

Use SHA1

import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.security.DigestInputStream;
import java.security.MessageDigest;
public class MainClass {
  private static int BUFFER_SIZE = 32 * 1024;
  public static void main(String[] args) throws Exception {
    System.out.println("test.txt: " + md("test.txt"));
  }
  public static String md(String f) throws Exception {
    BufferedInputStream file = new BufferedInputStream(new FileInputStream(f));
    MessageDigest md = MessageDigest.getInstance("SHA-1");
    DigestInputStream in = new DigestInputStream(file, md);
    int i;
    byte[] buffer = new byte[BUFFER_SIZE];
    do {
      i = in.read(buffer, 0, BUFFER_SIZE);
    } while (i == BUFFER_SIZE);
    md = in.getMessageDigest();
    in.close();
    return new String(md.digest());
  }
}