This question already has answers here:
Is it possible to decrypt MD5 hashes?
(24 answers)
Closed 7 years ago.
I want to encrypt a string value with md5 and then decrypt it so I so that it possible with a key. So I searched how to do this and I found only one other alghorithm.
This is the encryption class:
class crypt
{
public string encrypt(string bhash)
{
MD5 md5 = new MD5CryptoServiceProvider();
md5.ComputeHash(ASCIIEncoding.ASCII.GetBytes(bhash));
byte[] result = md5.Hash;
StringBuilder strBuilder = new StringBuilder();
for (int i = 0; i < result.Length; i++)
{
strBuilder.Append(result[i].ToString("x2"));
}
bhash = strBuilder.ToString();
return bhash;
}
}
The only way to decrypt an md5 encryption is through brute forcing all the possible original content.
There is no algorithm for decryption. You must test out all possible values and encrypt them and check for a match to find the original value.
Related
This question already has answers here:
MD5 hashing does not match in C# and PHP
(2 answers)
Closed 5 years ago.
in C# I'm trying to get a hashed md5 value of a password like so:
string sb = textBox2.Text;
byte[] asciiBytes = ASCIIEncoding.ASCII.GetBytes(sb);
byte[] hashedBytes = MD5CryptoServiceProvider.Create().ComputeHash(asciiBytes);
string hashedString = BitConverter.ToString(hashedBytes).Replace("-", "").ToLower();
var plainTextBytes = System.Text.Encoding.UTF8.GetBytes(sb);
sb = System.Convert.ToBase64String(plainTextBytes);
in php I get that value by using md5 command,
echo md5("megusia94");
the input in both cases are the same,
yet the output in PHP is: d1e44ad921daadaf8defadcd21c8644a
while in C# the output is: bWVndXMpYTk0
What am I doing wrong? I've searched this forum and tried:
MD5 hashing does not match in C# and PHP
c# md5 and php md5 not match
You are not comparing the same two things.
What you are comparing is the base64-representation of the ASCII-encoded input string with the actual MD5 hash (in HEX representation) from PHP.
Instead look at this:
byte[] asciiBytes = ASCIIEncoding.ASCII.GetBytes("megusia94");
byte[] hashedBytes = MD5CryptoServiceProvider.Create().ComputeHash(asciiBytes);
string hashedString = BitConverter.ToString(hashedBytes).Replace("-", "").ToLower();
Console.WriteLine(hashedString);
It correctly produces the hash d1e44ad921daadaf8defadcd21c8644a, which is the same as the one you get from PHP.
PHP md5:
Returns the hash as a 32-character hexadecimal number.
Your C# code:
Returns the hash with base64 encoding.
This question already has answers here:
Is it possible to decrypt MD5 hashes?
(24 answers)
Closed 6 years ago.
I am encrypting my password using below code.
public static string GetSHA1HashData(string password)
{
//create new instance of md5
SHA1 sha1 = SHA1.Create();
//convert the input text to array of bytes
byte[] hashData = sha1.ComputeHash(Encoding.Default.GetBytes(password));
//create new instance of StringBuilder to save hashed data
StringBuilder returnValue = new StringBuilder();
//loop for each byte and add it to StringBuilder
for (int i = 0; i < hashData.Length; i++)
{
returnValue.Append(hashData[i].ToString());
}
// return hexadecimal string
return returnValue.ToString();
}
But I also want to create code for Decryption. I've tried, but couldn't a good solution. So could you help me on this?
Here I used System.Security.Cryptography => SHA1 : HashAlgorithm
Thanks in advance.
Hash value can't be decrypted:
Hash is short (say, 256-bit only), while String is arbitrary long (up to 2GB), so there're many Strings with the same hash (ambiguity)
Hash algorithm (SHA1) has been specially designed such that it's a difficult task to find out a string that has given hash value (complexity)
Instead of decrypting, compare hash values: if user provides a password that has the same hash value that a stored hash, then the password is correct one.
This question already has answers here:
How can I unhash a hash using C#?
(4 answers)
Closed 8 years ago.
I have this asp.net project that I need to hash the password (preferably with salt) and save it in sql database then unhash it for comparing with the login password or sth like that....
the thing is I'm not sure what is the best way to do it in a most secure way and how can I code this in C#?
You do not unhash. That's the point of hashing: it cannot be reversed.
You look up the salt, then you hash the password that they entered together with the salt. If the hash is the same as the hash in the database, it's a valid login.
Maybe take a look here:
Salted password hashing
First of all you cannot recover the hashed data. Its one way process. But you can match hashed data. To do so check the code given below :
Do this inside your button click event
string salt = GetSalt(10); // 10 is the size of Salt
string hashedPass = HashPassword(salt, Password.Text);
This are the functions that will help your to hash the password
const string alphanumeric = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890";
public static string GetSalt(int saltSize)
{
Random r = new Random();
StringBuilder strB = new StringBuilder("");
while ((saltSize--) > 0)
strB.Append(alphanumeric[(int)(r.NextDouble() * alphanumeric.Length)]);
return strB.ToString();
}
public static string HashPassword(string salt, string password)
{
string mergedPass = string.Concat(salt, password);
return EncryptUsingMD5(mergedPass);
}
public static string EncryptUsingMD5(string inputStr)
{
using (MD5 md5Hash = MD5.Create())
{
// Convert the input string to a byte array and compute the hash.
byte[] data = md5Hash.ComputeHash(Encoding.UTF8.GetBytes(inputStr));
// Create a new Stringbuilder to collect the bytes
// and create a string.
StringBuilder sBuilder = new StringBuilder();
// Loop through each byte of the hashed data
// and format each one as a hexadecimal string.
for (int i = 0; i < data.Length; i++)
sBuilder.Append(data[i].ToString("x2"));
// Return the hexadecimal string.
return sBuilder.ToString();
}
}
Similarly, when you try to match the password to authenticate the user, perform the same method just fetch your hashed password from your database and compare them. If the entered hashed password matches the database hashed password, its an authorized user.
Updated :
When you hash the password of the user for the first time and then store into database in the same table store the salt for that user.
Next time when you try to compare the password, fetch that salt of the user from the database and hash it using to compare with the
hashed password in the database.
Hope that answers your Question.
On my Blackberry I am creating an AES key and encrypting data. I am then encrypting the AES key with RSA before sending to the client c#.net
The AES key is a byte array. How can I convert this to a string so that it can be encrypted by RSA and then decrypted on the .net side?
Do I have to convert to string?
I am transmitting the data via JSON. I guess my question is really how to transmit a but array in JSON? What character encoding would I use?
Thanks.
You can use the following, which is URL safe and relatively easy to visually inspect. This takes a little more storage than Convert.ToBase64String, but shouldn't be an issue with a fixed width encryption key.
string MyKey = BitConverter.ToString(MyAESKey); // dash removal is trivial here
OR
string MyKey = Convert.ToBase64String(MyAESKey);
Code Sample
byte[] a = new byte[256/8];
Random random = new Random();
random.NextBytes(a);
string base64 = Convert.ToBase64String(a);
byte [] b = Convert.FromBase64String(base64);
if (a.SequenceEqual(b))
// true
string c = BitConverter.ToString(a);
string[] c1 = c.Split('-');
byte[] d = new byte[arr.Length];
for (int i = 0; i < arr.Length; i++) d[i] = Convert.ToByte(c1[i], 16);
if (a.SequenceEqual(d))
// true
MD5 md5 = MD5.Create();
byte[] Ostring = System.Text.Encoding.UTF8.GetBytes("original string");
byte[] hashMD5 = md5.ComputeHAsh(Ostring);
StringBuilder sb = new StringBuilder();
for (int i=0; i<hashMD5.Length; i++)
{
sb.Append(hashMD5[i].ToString("X2"));
}
string strMD5 = sb.ToString();
the value of strMD5 I want encrypt it, using the algorithm RSA with a key in DER format "file: aa.key"
How I can do it in c #?
Your code only hashes a string. Hashes are asymmetrical, one-way only - you cannot "unhash" something.
A good, complete example of symmetrical string encryption is here: http://www.obviex.com/samples/Encryption.aspx.
I show an extended example here
The context in this sample was to encrypt a query string using c#