Encrypt and Decrypt Md5

Md5 hash encryption and decryption

MD5 has been proven to be a weak algorithm. As all your 'passwords' are basic, the website has already stored each password with a hash that was cracked long ago.

You cannot decrypt a hash, but you can brute-force and find out what it is.

Read more here:
https://en.wikipedia.org/wiki/MD5

and

here:
https://security.stackexchange.com/questions/19906/is-md5-considered-insecure

EDIT: Saw that you updated your question.

Assuming that you were to have a complex password of 'ajfn3inf'
and you were to hash it. Running a md5 cracker will be easy to unhash it due to it's relatively short length and the power of GPU's to crack a hash. Read the links above to understand more about MD5.

Is it possible to decrypt MD5 hashes?

No. MD5 is not encryption (though it may be used as part of some encryption algorithms), it is a one way hash function. Much of the original data is actually "lost" as part of the transformation.

Think about this: An MD5 is always 128 bits long. That means that there are 2¹²⁸ possible MD5 hashes. That is a reasonably large number, and yet it is most definitely finite. And yet, there are an infinite number of possible inputs to a given hash function (and most of them contain more than 128 bits, or a measly 16 bytes). So there are actually an infinite number of possibilities for data that would hash to the same value. The thing that makes hashes interesting is that it is incredibly difficult to find two pieces of data that hash to the same value, and the chances of it happening by accident are almost 0.

A simple example for a (very insecure) hash function (and this illustrates the general idea of it being one-way) would be to take all of the bits of a piece of data, and treat it as a large number. Next, perform integer division using some large (probably prime) number n and take the remainder (see: Modulus). You will be left with some number between 0 and n. If you were to perform the same calculation again (any time, on any computer, anywhere), using the exact same string, it will come up with the same value. And yet, there is no way to find out what the original value was, since there are an infinite number of numbers that have that exact remainder, when divided by n.

That said, MD5 has been found to have some weaknesses, such that with some complex mathematics, it may be possible to find a collision without trying out 2¹²⁸ possible input strings. And the fact that most passwords are short, and people often use common values (like "password" or "secret") means that in some cases, you can make a reasonably good guess at someone's password by Googling for the hash or using a Rainbow table. That is one reason why you should always "salt" hashed passwords, so that two identical values, when hashed, will not hash to the same value.

Once a piece of data has been run through a hash function, there is no going back.

Can I Decrypt md5 in php?

MD5 is a hash function, which are one-way functions (cannot be undone).

Whilst I would not recommend MD5 for password storage, if you want to verify that a password is correct you do not need to decrypt the hash. The idea is in order to verify a password is correct, rather than decrypting the hash, you encrypt the password given and compare the two hash values. If the two hash values are the same, then the two passwords are the same,

md5 encryption and decryption java unable to encrypt more than 16bytes

Hi you are not doing MD5 Encryption, you are getting the MD5 Digest of a String and then using it to generate a Key that does DESede/CBC Encryption for you. Kindly note that MD5 is not an Encryption but a Hashing Algorithm. Details available at this Link

Hashing is one way . You can not get convert your data/ string from a hash code. Encryption is 2 way - you can decrypt again the encrypted string if you have the key with you. Encryption function transforms a text into a nonsensical ciphertext by using an encryption key, and vice versa.

Instead of doing a decipher.update(..) you need a doFinal(..) , and also instead of converting the encrytped byte[] to String, try returning a byte[] from encrypt and pass a byte[] to decrypt as parameter; the way it is meant to be use. Below should solve your problem :

import java.security.MessageDigest;
import java.util.Arrays;
import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
public class Md5Encryption 
{
    private static final String ALGORITHM = "md5";
    private static final String DIGEST_STRING = "HG58YZ3CR9";
    private static final String CHARSET_UTF_8 = "utf-8";
    private static final String SECRET_KEY_ALGORITHM = "DESede";
    private static final String TRANSFORMATION_PADDING = "DESede/CBC/PKCS5Padding";

    /* Encryption Method */
    public byte[] encrypt(String message) throws Exception 
    { 
        final MessageDigest md = MessageDigest.getInstance(ALGORITHM); 
        final byte[] digestOfPassword = md.digest(DIGEST_STRING.getBytes(CHARSET_UTF_8)); 
        final byte[] keyBytes = Arrays.copyOf(digestOfPassword, 24); 
        for (int j = 0, k = 16; j < 8;) { 
                keyBytes[k++] = keyBytes[j++]; 
        } 

        final SecretKey key = new SecretKeySpec(keyBytes, SECRET_KEY_ALGORITHM); 
        final IvParameterSpec iv = new IvParameterSpec(new byte[8]); 
        final Cipher cipher = Cipher.getInstance(TRANSFORMATION_PADDING); 
        cipher.init(Cipher.ENCRYPT_MODE, key, iv); 

        final byte[] plainTextBytes = message.getBytes(CHARSET_UTF_8); 
        final byte[] cipherText = cipher.doFinal(plainTextBytes); 

        return cipherText; 
    } 

   /* Decryption Method */
    public String decrypt(byte[]  message) throws Exception { 
        final MessageDigest md = MessageDigest.getInstance(ALGORITHM); 
        final byte[] digestOfPassword = md.digest(DIGEST_STRING.getBytes(CHARSET_UTF_8)); 
        final byte[] keyBytes = Arrays.copyOf(digestOfPassword, 24); 
        for (int j = 0, k = 16; j < 8;) { 
                keyBytes[k++] = keyBytes[j++]; 
        } 

        final SecretKey key = new SecretKeySpec(keyBytes, SECRET_KEY_ALGORITHM); 
        final IvParameterSpec iv = new IvParameterSpec(new byte[8]); 
        final Cipher decipher = Cipher.getInstance(TRANSFORMATION_PADDING); 
        decipher.init(Cipher.DECRYPT_MODE, key, iv); 

        final byte[] plainText = decipher.doFinal(message); 

        return new String(plainText, CHARSET_UTF_8); 
    }

    public static void main(String[] args) throws Exception {


        String text = "TEST STRING TO ENCRYPT";
        byte[] codedtext = new Md5Encryption().encrypt(text);
//        String codedtext = ".ªÉ…U$L§U`8ˉ­?¦”›°„";
        String decodedtext = new Md5Encryption().decrypt(codedtext); 

        System.out.println(codedtext); // this is a byte array, you'll just see a reference to an array 
        System.out.println(decodedtext); // This correctly shows "TEST STRING TO ENCRYPT" 
    } 


}

Dencryption of md5 string in Go

You don't

MD5 is a hash function, not an encryption function. The point of a hash function is that it is impossible to convert the output back into the input

md5 Encryption and decryption

Basically, MD5 is not an encryption method.

It's a Hash function, where you will lose the data due to the data processing under the function. So you wont get the old data back. So the whole point of a hash is that it's one way only. MD5 is http://en.wikipedia.org/wiki/Cryptographic_hash_function">cryptographic hash function so the following things are applicable.

Some people save the user passwords using the MD5 Hash. So, even their webservers won't be knowing what exactly is your password. They only have a token for the password. Thats why in many of the websites when you request a forgot-password request, they asks you to change the password by providing a unique link instead of retrieving your old password. (Basically, they don't have your password in human readable format)

So another doubt that you could have is what if someone knows your hashed password token? The answer is simple, still you are safe, because the login authentication check converts the user input to a hash function and then checks with the DB. In this case, a new Hash value will be obtained for your hashed value.

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