&gt; **Possible Duplicate:**  
&gt; [Forgot Password: what is the best method of implementing a forgot password function?](https://stackoverflow.com/questions/522967/forgot-password-what-is-the-best-method-of-implementing-a-forgot-password-funct)  

&lt;!-- End of automatically inserted text --&gt;

I&#39;m programming a community website.

I want to build a &quot;forgot my password&quot; feature.

Looking around at different sites, I&#39;ve found they employ one of **three options**:

1. send the user an **email with a link to a unique, hidden URL** that allows him to change his password (Gmail and Amazon)

2. send the user an email with a **new, randomly generated password** (Wordpress)

3. send the user **his current password** (www.teach12.com)

**Option #3** seems the most convenient to the user but since I save passwords as an MD5 hash, I don&#39;t see how option #3 would be available to me since **MD5 is irreversible**. This also seems to be **insecure** option since it means that the website must be saving the password in clear text somewhere, and at the least the clear-text password is being sent over insecure e-mail to the user. Or am I missing something here?

So if I can&#39;t do option #1, **option #2** seems to be the **simplest to program** since I just have to change the user&#39;s password and send it to him. Although this is **somewhat insecure** since you have to have a live password being communicated via insecure e-mail. However, this could also be misused by trouble-makers to **pester users** by typing in random e-mails and constantly changing passwords of various users.

**Option #1** seems to be the **most secure** but requires a little extra programming to deal with a hidden URL that expires etc., but it seems to be what the big sites use.

**What experience have you had using/programming these various options? Are there any options I&#39;ve missed?**


What is the best &quot;forgot my password&quot; method?

I want to compute an md5 hash not of a string, but of an entire data structure.  I understand the mechanics of a way to do this (dispatch on the type of the value, canonicalize dictionary key order and other randomness, recurse into sub-values, etc).  But it seems like the kind of operation that would be generally useful, so I&#39;m surprised I need to roll this myself.  

Is there some simpler way in Python to achieve this?

UPDATE: pickle has been suggested, and it&#39;s a good idea, but pickling doesn&#39;t canonicalize dictionary key order:

    &gt;&gt;&gt; import cPickle as pickle
    &gt;&gt;&gt; import hashlib, random 
    &gt;&gt;&gt; for i in range(10):
    ...  k = [i*i for i in range(1000)]
    ...  random.shuffle(k)
    ...  d = dict.fromkeys(k, 1)
    ...  p = pickle.dumps(d)
    ...  print hashlib.md5(p).hexdigest()
    ...
    51b5855799f6d574c722ef9e50c2622b
    43d6b52b885f4ecb4b4be7ecdcfbb04e
    e7be0e6d923fe1b30c6fbd5dcd3c20b9
    aebb2298be19908e523e86a3f3712207
    7db3fe10dcdb70652f845b02b6557061
    43945441efe82483ba65fda471d79254
    8e4196468769333d170b6bb179b4aee0
    951446fa44dba9a1a26e7df9083dcadf
    06b09465917d3881707a4909f67451ae
    386e3f08a3c1156edd1bd0f3862df481

Computing an md5 hash of a data structure

When I try to get the MD5 fingerprint using `keytool`, I get a SHA1 fingerprint instead and the Google Maps doesn&#39;t recognize it. How do I get the MD5 fingerprint?

Google Maps API for Android, getting SHA1 cert instead of MD5

There are many MD5 JavaScript implementations out there. 
Does anybody know which one is the most advanced, most bugfixed and fastest? 

I need it for [this][1] tool.


  [1]: http://www.bruechner.de/md5file/js/

fastest MD5 Implementation in JavaScript

Given two different messages, A and B (maybe 20-80 characters of text, if size matters at all), what is the probability that the MD5 digest of A is the same as the MD5 digest of B *and* the SHA1 digest of A is the same as the SHA1 digest of B?  That is:

    (MD5(A) == MD5(B)) &amp;&amp; (SHA1(A) == SHA1(B))

Assume no malicious intent, i.e., that the messages are not selected with an aim of finding a clash.  I just want to know the odds of this happening naturally.

I&#39;m thinking the chances are &quot;astronomically low,&quot; but I&#39;m not sure how to verify this.

More information: the size of the pool of possible messages is restricted, but large (several hundred million).  Birthday paradox situations are exactly what I&#39;m worried about.


What are the chances that two messages have the same MD5 digest and the same SHA1 digest?

I&#39;m not a programmer, just a regular user of Google Drive. I want to see if the files are uploaded correctly. I go through a whole process in the OAuth 2.0 Playground that lists all files, shows the MD5 checksums but also lots of information per file. If I upload a new file it&#39;s hard to search for it and verify its md5 checksum.

Is there an easier way (through an app, maybe?) to show/list MD5 checksums for the uploaded files? I wonder why the Details pane doesn&#39;t have it, only lists the file size in bytes.

Google Drive MD5 checksum for files

Someone told me that he has seen software systems that:

 1. retrieve MD5 encrypted passwords from other systems;
 2. decrypt the encrypted passwords and
 3. store the passwords in the database of the system using the systems own algorithm.

Is that possible? I thought that it wasn&#39;t possible / feasible to decrypt MD5 hashes.

I know there are MD5 dictionaries, but is there an actual decryption algorithm?

Is it possible to decrypt MD5 hashes?

Is there any method to generate MD5 hash of a string in Java?

How can I generate an MD5 hash in Java?

I have used hashlib (which replaces md5 in Python 2.6/3.0) and it worked fine if I opened a file and put its content in [`hashlib.md5()`][1] function.

The problem is with very big files that their sizes could exceed RAM size.

How to get the MD5 hash of a file without loading the whole file to memory?


  [1]: https://docs.python.org/2/library/hashlib.html

Get MD5 hash of big files in Python

I have written a simple Java class to generate the hash values of the Windows Calculator file.  I am using `Windows 7 Professional with SP1`.  I have tried `Java 6.0.29` and `Java 7.0.03`.  Can someone tell me why I am getting different hash values from Java versus (many!) external utilities and/or websites?  Everything external matches with each other, only Java is returning different results.

    import java.io.File;
    import java.io.FileInputStream;
    import java.io.FileNotFoundException;
    import java.io.IOException;
    import java.util.LinkedHashMap;
    import java.util.Map;
    import java.util.Map.Entry;
    import java.util.zip.CRC32;
    import java.security.DigestInputStream;
    import java.security.MessageDigest;
    import java.security.NoSuchAlgorithmException;
    
    public class Checksum 
    {
        private static int size = 65536;
        private static File calc = new File(&quot;C:/Windows/system32/calc.exe&quot;);
    
        /*
            C:\Windows\System32\calc.exe (verified via several different utilities)
            ----------------------------
            CRC-32b = 8D8F5F8E
            MD5     = 60B7C0FEAD45F2066E5B805A91F4F0FC
            SHA-1   = 9018A7D6CDBE859A430E8794E73381F77C840BE0
            SHA-256 = 80C10EE5F21F92F89CBC293A59D2FD4C01C7958AACAD15642558DB700943FA22
            SHA-384 = 551186C804C17B4CCDA07FD5FE83A32B48B4D173DAC3262F16489029894FC008A501B50AB9B53158B429031B043043D2
            SHA-512 = 68B9F9C00FC64DF946684CE81A72A2624F0FC07E07C0C8B3DB2FAE8C9C0415BD1B4A03AD7FFA96985AF0CC5E0410F6C5E29A30200EFFF21AB4B01369A3C59B58
        
    
            Results from this class
            -----------------------
            CRC-32  = 967E5DDE
            MD5     = 10E4A1D2132CCB5C6759F038CDB6F3C9
            SHA-1   = 42D36EEB2140441B48287B7CD30B38105986D68F
            SHA-256 = C6A91CBA00BF87CDB064C49ADAAC82255CBEC6FDD48FD21F9B3B96ABF019916B    
        */    
    
        public static void main(String[] args)throws Exception {
            Map&lt;String, String&gt; hashes = getFileHash(calc);
            for (Map.Entry&lt;String, String&gt; entry : hashes.entrySet()) {
                System.out.println(String.format(&quot;%-7s = %s&quot;, entry.getKey(), entry.getValue()));
            }
        }
        
        private static Map&lt;String, String&gt; getFileHash(File file) throws NoSuchAlgorithmException, IOException {
            Map&lt;String, String&gt; results = new LinkedHashMap&lt;String, String&gt;();
    
            if (file != null &amp;&amp; file.exists()) {
                CRC32 crc32 = new CRC32();
                MessageDigest md5 = MessageDigest.getInstance(&quot;MD5&quot;);
                MessageDigest sha1 = MessageDigest.getInstance(&quot;SHA-1&quot;);
                MessageDigest sha256 = MessageDigest.getInstance(&quot;SHA-256&quot;);
                
                FileInputStream fis = new FileInputStream(file);
                byte data[] = new byte[size];
                int len = 0;
                while ((len = fis.read(data)) != -1) {
                    crc32.update(data, 0, len);
                    md5.update(data, 0, len);
                    sha1.update(data, 0, len);
                    sha256.update(data, 0, len);
                }
                fis.close();
    
                results.put(&quot;CRC-32&quot;, toHex(crc32.getValue()));
                results.put(md5.getAlgorithm(), toHex(md5.digest()));
                results.put(sha1.getAlgorithm(), toHex(sha1.digest()));
                results.put(sha256.getAlgorithm(), toHex(sha256.digest()));
            }
            return results;
        }
    
        private static String toHex(byte[] bytes) {
            String result = &quot;&quot;;
            if (bytes != null) {
                StringBuilder sb = new StringBuilder(bytes.length * 2);
                for (byte element : bytes) {
                    if ((element &amp; 0xff) &lt; 0x10) {
                        sb.append(&quot;0&quot;);
                    }
                    sb.append(Long.toString(element &amp; 0xff, 16));
                }
                result = sb.toString().toUpperCase();
            }
            return result;
        }
    
        private static String toHex(long value) {
            return Long.toHexString(value).toUpperCase();
        }
    
    }

Different results with Java&#39;s digest versus external utilities

What is the maximum length of the string that can have md5 hashed? Or: If it has no limit, and if so what will be the max length of the md5 output value?

Maximum length for MD5 input/output

I use the following C# code to calculate a MD5 hash from a string.
It works well and generates a 32-character hex string like this:
`900150983cd24fb0d6963f7d28e17f72`
 
&lt;!-- language: c# --&gt;

    string sSourceData;
    byte[] tmpSource;
    byte[] tmpHash;
    sSourceData = &quot;MySourceData&quot;;

    //Create a byte array from source data.
    tmpSource = ASCIIEncoding.ASCII.GetBytes(sSourceData);
    tmpHash = new MD5CryptoServiceProvider().ComputeHash(tmpSource);

    // and then convert tmpHash to string...
 
Is there a way to use code like this to generate a 16-character hex string (or 12-character string)? A 32-character hex string is good but I think it&#39;ll be boring for the customer to enter the code!

Calculate a MD5 hash from a string

&gt; **Possible Duplicate:**  
&gt; [Generate a Hash from string in Javascript/jQuery](https://stackoverflow.com/questions/7616461/generate-a-hash-from-string-in-javascript-jquery)  

&lt;!-- End of automatically inserted text --&gt;

Can anyone suggest a simple (i.e. tens of lines of code, not hundreds of lines) hash function written in (browser-compatible) JavaScript?  Ideally I&#39;d like something that, when passed a string as input, produces something similar to the 32 character hexadecimal string that&#39;s the typical output of MD5, SHA1, etc.  It doesn&#39;t have to be cryptographically secure, just reasonably resistant to collisions.  (My initial use case is URLs, but I&#39;ll probably want to use it on other strings in the future.)

Simple (non-secure) hash function for JavaScript?

I&#39;m working with some example java code for making md5 hashes. One part converts the results from bytes to a string of hex digits:

    byte messageDigest[] = algorithm.digest();     
    StringBuffer hexString = new StringBuffer();
    for (int i=0;i&lt;messageDigest.length;i++) {
        hexString.append(Integer.toHexString(0xFF &amp; messageDigest[i]));
        }

However, it doesn&#39;t quite work since toHexString apparently drops off leading zeros. So, what&#39;s the simplest way to go from byte array to hex string that maintains the leading zeros?

In Java, how do I convert a byte array to a string of hex digits while keeping leading zeros?

I&#39;ve got an image library on Amazon S3. For each image, I md5 the source URL on my server plus a timestamp to get a unique filename. Since S3 can&#39;t have subdirectories, I need to store all of these images in a single flat folder.

Do I need to worry about collisions in the MD5 hash value that gets produced?

Bonus: How many files could I have before I&#39;d start seeing collisions in the hash value that MD5 produces?

How many random elements before MD5 produces collisions?

I want python to read to the EOF so I can get an appropriate hash, whether it is sha1 or md5. Please help. Here is what I have so far:

    import hashlib

    inputFile = raw_input(&quot;Enter the name of the file:&quot;)
    openedFile = open(inputFile)
    readFile = openedFile.read()

    md5Hash = hashlib.md5(readFile)
    md5Hashed = md5Hash.hexdigest()

    sha1Hash = hashlib.sha1(readFile)
    sha1Hashed = sha1Hash.hexdigest()

    print &quot;File Name: %s&quot; % inputFile
    print &quot;MD5: %r&quot; % md5Hashed
    print &quot;SHA1: %r&quot; % sha1Hashed

Hashing a file in Python

Is MD5 hashing a file still considered a good enough method to uniquely identify it given all the breaking of MD5 algorithm and security issues etc? Security is not my primary concern here, but uniquely identifying each file is. 

Any thoughts?

Is MD5 still good enough to uniquely identify files?

I&#39;m making a php login, and I&#39;m trying to decide whether to use SHA1 or Md5, or SHA256 which I read about in another stackoverflow article. Are any of them more secure than others? For SHA1/256, do I still use a salt? 

Also, is this a secure way to store the password as a hash in mysql?

    function createSalt()
    {
        $string = md5(uniqid(rand(), true));
        return substr($string, 0, 3);
    }
    
    $salt = createSalt();
     
    $hash = sha1($salt . $hash);



SHA1 vs md5 vs SHA256: which to use for a PHP login?

Is calculating an MD5 hash less CPU intensive than SHA-1 or SHA-2 on &quot;standard&quot; laptop x86 hardware? I&#39;m interested in general information, not specific to a certain chip.

**UPDATE:**
In my case, I&#39;m interested in calculating the hash of a file. If file-size matters, let&#39;s assume its 300K.

Is calculating an MD5 hash less CPU intensive than SHA family functions?

I have written some code in Python that checks for an MD5 hash in a file and makes sure the hash matches that of the original. 

Here is what I have developed:

    # Defines filename
    filename = &quot;file.exe&quot;

    # Gets MD5 from file 
    def getmd5(filename):
        return m.hexdigest()

    md5 = dict()

    for fname in filename:
        md5[fname] = getmd5(fname)

    # If statement for alerting the user whether the checksum passed or failed
    
    if md5 == &#39;&gt;md5 will go here&lt;&#39;: 
        print(&quot;MD5 Checksum passed. You may now close this window&quot;)
        input (&quot;press enter&quot;)
    else:
        print(&quot;MD5 Checksum failed. Incorrect MD5 in file &#39;filename&#39;. Please download a new copy&quot;)
        input(&quot;press enter&quot;) 
    exit


But whenever I run the code, I get the following error:

    Traceback (most recent call last):
    File &quot;C:\Users\Username\md5check.py&quot;, line 13, in &lt;module&gt;
     md5[fname] = getmd5(fname)
    File &quot;C:\Users\Username\md5check.py, line 9, in getmd5
      return m.hexdigest()
    NameError: global name &#39;m&#39; is not defined

Is there anything I am missing in my code?

How do I calculate the MD5 checksum of a file in Python?

How to calculate the MD5 in Objective-C?




MD5 algorithm in Objective-C

What is the best way to generate an MD5 (or any other hash) of a multi-dimensional array? 

I could easily write a loop which would traverse through each level of the array, concatenating each value into a string, and simply performing the MD5 on the string. 

However, this seems cumbersome at best and I wondered if there was a funky function which would take a multi-dimensional array, and hash it.

PHP best way to MD5 multi-dimensional array?

I want to convert a string like &quot;abc&quot; to an MD5 hash. I want to do this in iOS and Swift. I have tried using the solutions below but they were not working for me:

https://stackoverflow.com/questions/25248598/importing-commoncrypto-in-a-swift-framework

https://stackoverflow.com/questions/24123518/how-to-use-cc-md5-method-in-swift-language

http://iosdeveloperzone.com/2014/10/03/using-commoncrypto-in-swift/

To be more clear, I want to achieve an output in Swift similar to this PHP code&#39;s output:

    $str = &quot;Hello&quot;;
    
    echo md5($str);

Output: 8b1a9953c4611296a827abf8c47804d7

How can I convert a String to an MD5 hash in iOS using Swift?

I read some docs about md5, it said that its 128 bits, but why is it 32 characters? I can&#39;t compute the characters.

* 1 byte is 8 bits
* if 1 character is 1 byte
* then 128 bits is 128/8 = 16 bytes right?

EDIT:

SHA-1 produces 160 bits, so how many characters are there?

MD5 is 128 bits but why is it 32 characters?

What is the **easiest** way to generate a random hash (MD5) in Python?

Random hash in Python

I am looking to use Java to get the MD5 checksum of a file.  I was really surprised but I haven&#39;t been able to find anything that shows how to get the MD5 checksum of a file.

How is it done?

Getting a File&#39;s MD5 Checksum in Java

Is there a fixed point in the MD5 transformation, i.e. does there exist x such that `md5(x) == x`?

Is there an MD5 Fixed Point where md5(x) == x?

Is there a way to calculate the MD5 hash of a file before the upload to the server using Javascript?

How to calculate md5 hash of a file using javascript

As I want to use Google maps in my application, I need the debug certificates&#39; MD5 fingerprint. I tried following.: 

(Here I copied the debug.keystore file from C:\Documents and Settings\Administrator\.android in bin folder)

    C:\Program Files\Java\jdk1.7.0\bin&gt;keytool -list -alias androiddebugkey -keystore debug.keystore -storepass android -keypass android

But got the following results:

    androiddebugkey, May 27, 2011, PrivateKeyEntry,Certificate fingerprint (SHA1): &quot;some code&quot;

However that is not working to get MAP API key. Is SHA1 is same as MD5?

What should I do to get the MD5 certificate?

How can I get the MD5 fingerprint from Java&#39;s keytool, not only SHA-1?

For each of our binary assets we generate a MD5 hash. This is used to check whether a certain binary asset is already in our application. But is it possible that two different binary assets generate the same MD5 hash. So is it possible that two different strings generate the same MD5 hash?

Can two different strings generate the same MD5 hash code?

One concept I&#39;ve always wondered about is the use of cryptographic hash functions and values. I understand that these functions can generate a hash value that is unique and virtually impossible to reverse, but here&#39;s what I&#39;ve always wondered:

If on my server, in PHP I produce:

    md5(&quot;stackoverflow.com&quot;) = &quot;d0cc85b26f2ceb8714b978e07def4f6e&quot;

When you run that same string through an MD5 function, you get the same result on your PHP installation. A process is being used to produce some value, from some starting value.

Doesn&#39;t this mean that there is some way to deconstruct what is happening and reverse the hash value? 

What is it about these functions that makes the resulting strings impossible to retrace?


How come MD5 hash values are not reversible?

I know that SHA-256 is favored over MD5 for security, etc., but, if I am to use a method to only check file integrity (that is, nothing to do with password encryption, etc.), is there any advantage of using SHA-256?

Since MD5 is 128-bit and SHA-256 is 256-bit (therefore twice as big)...

1. Would it take up to twice as long to encrypt?

2. Where time is not of essence, like in a backup program, and file integrity is all that is needed, would anyone argue against MD5 for a different algorithm, or even suggest a different technique?

3. Does using MD5 produce a checksum?


SHA-256 or MD5 for file integrity

I have a simple android client which needs to &#39;talk&#39; to a simple C# HTTP listener. I want to provide a basic level of authentication by passing username/password in POST requests.

MD5 hashing is trivial in C# and provides enough security for my needs but I can&#39;t seem to find how to do this at the android end.

EDIT: Just to address the concerns raised about MD5 weakness - the C# server runs on the PCs of the users of my android client. In many cases, they&#39;ll be accessing the server using wi-fi on their own LANs but, at their own risk, they may choose to access it from the internet. Also the service on the server needs to use pass-through for the MD5 to a 3rd party application I have no control over.

MD5 hashing in Android

How to write `functionToGenerateMD5hash` for this code? I already have `fileVideo` and I need to send the corresponding md5 hash to the server by clicking on the button.

    $(&quot;#someButton&quot;).click(function() {
    var fr = new FileReader();      
    fr.onload = function(e) {            
        string md5 = functionToGenerateMD5hash(e.target.result);
        // send md5 here
    };       
    fr.readAsArrayBuffer(fileVideo);

Also, can you use this to generate a MD5 hash in Node.js?

How to generate an MD5 file hash in JavaScript/Node.js?

I am uploading a file to S3 using Java - this is what I got so far:

    AmazonS3 s3 = new AmazonS3Client(new BasicAWSCredentials(&quot;XX&quot;,&quot;YY&quot;));
    						
    List&lt;Bucket&gt; buckets = s3.listBuckets();
    						
    s3.putObject(new PutObjectRequest(buckets.get(0).getName(), fileName, stream, new ObjectMetadata()));

The file is being uploaded but a WARNING is raised when I am not setting the content length:

&gt;     com.amazonaws.services.s3.AmazonS3Client putObject: No content length specified for stream &gt; data.  Stream contents will be buffered in memory and could result in out of memory errors.

This is a file I am uploading and the `stream` variable is an `InputStream`, from which I can get the byte array like this: `IOUtils.toByteArray(stream)`.

So when I try to set the content length and MD5 (taken from [here][1]) like this:

    // get MD5 base64 hash
    MessageDigest messageDigest = MessageDigest.getInstance(&quot;MD5&quot;);
    messageDigest.reset();
    messageDigest.update(IOUtils.toByteArray(stream));
    byte[] resultByte = messageDigest.digest();
    String hashtext = new String(Hex.encodeHex(resultByte));

    ObjectMetadata meta = new ObjectMetadata();
    meta.setContentLength(IOUtils.toByteArray(stream).length);
    meta.setContentMD5(hashtext);

**It causes the following error to come back from S3:**

&gt; The Content-MD5 you specified was invalid.

What am I doing wrong?

Any help appreciated!

**P.S.** I am on Google App Engine - I cannot write the file to disk or [create a temp file][2] because AppEngine does not support FileOutputStream.


  [1]: https://stackoverflow.com/questions/415953/generate-md5-hash-in-java
  [2]: http://www.java2s.com/Code/JavaAPI/java.io/FilecreateTempFileStringprefixStringsuffix.htm

AmazonS3 putObject with InputStream length example

How can I convert the hashed result, which is a byte array, to a string?

    byte[] bytePassword = Encoding.UTF8.GetBytes(password);

    using (MD5 md5 = MD5.Create())
    {
        byte[] byteHashedPassword = md5.ComputeHash(bytePassword);
    } 

I need to convert `byteHashedPassword` to a string. 

Converting a md5 hash byte array to a string

This is how I started to get a `md5` hash from a `string`:

    import &quot;crypto/md5&quot;
    
    var original = &quot;my string comes here&quot;
    var hash = md5.New(original)

But obviously this is not how it works. Can someone provide me a working sample for this?

How to get a MD5 hash from a string in Golang?

Is there any simple way of generating (and checking) MD5 checksums of a list of files in Python? (I have a small program I&#39;m working on, and I&#39;d like to confirm the checksums of the files).

Generating an MD5 checksum of a file

How can I encrypt a string with MD5 in Rails 3.0 ?
`pass = MD5.hexdigest(pass)`  in a model yields `uninitialized constant MyModel::MD5`



RoR - MD5 generation

I&#39;ve the file path. How can I get the MD5 hash of it?


How to get the MD5 hash of a file in C++?

I&#39;m working on the [Google Cloud Storage .NET client
library][1]. There are three features (between .NET, my client
library, and the Storage service) that are combining in an
unpleasant way:

- When downloading files (objects in Google Cloud Storage
terminology), the server includes a hash of the stored data. My
client code then validates that hash against the data it&#39;s
downloaded.

- A separate feature of Google Cloud Storage is that the user can
set the Content-Encoding of the object, and that&#39;s included as a
header when downloading, when the request contains a matching
Accept-Encoding. (For the moment, let&#39;s ignore the behavior when the
request doesn&#39;t include that...)

- `HttpClientHandler` can decompress gzip (or deflate) content
automatically and transparently.

When all three of these are combined, we get into trouble. Here&#39;s a
short but complete program demonstrating that, but without using my
client library (and hitting a publicly accessible file):

    using System;
    using System.Linq;
    using System.Net;
    using System.Net.Http;
    using System.Security.Cryptography;
    using System.Text;
    using System.Threading.Tasks;
    
    class Program
    {
        static async Task Main()
        {
            string url = &quot;https://www.googleapis.com/download/storage/v1/b/&quot;
                + &quot;storage-library-test-bucket/o/gzipped-text.txt?alt=media&quot;;
            var handler = new HttpClientHandler
            {
                AutomaticDecompression = DecompressionMethods.GZip
            };
            var client = new HttpClient(handler);
            
            var response = await client.GetAsync(url);
            byte[] content = await response.Content.ReadAsByteArrayAsync();
            string text = Encoding.UTF8.GetString(content);
            Console.WriteLine($&quot;Content: {text}&quot;);
            
            var hashHeader = response.Headers.GetValues(&quot;X-Goog-Hash&quot;).FirstOrDefault();
            Console.WriteLine($&quot;Hash header: {hashHeader}&quot;);
            
            using (var md5 = MD5.Create())
            {
                var md5Hash = md5.ComputeHash(content);
                var md5HashBase64 = Convert.ToBase64String(md5Hash);
                Console.WriteLine($&quot;MD5 of content: {md5HashBase64}&quot;);
            }
        }
    }

.NET Core project file:

    &lt;Project Sdk=&quot;Microsoft.NET.Sdk&quot;&gt;
      &lt;PropertyGroup&gt;
        &lt;OutputType&gt;Exe&lt;/OutputType&gt;
        &lt;TargetFramework&gt;netcoreapp2.0&lt;/TargetFramework&gt;
        &lt;LangVersion&gt;7.1&lt;/LangVersion&gt;
      &lt;/PropertyGroup&gt;
    &lt;/Project&gt;

Output:

    Content: hello world
    Hash header: crc32c=T1s5RQ==,md5=xhF4M6pNFRDQnvaRRNVnkA==
    MD5 of content: XrY7u+Ae7tCTyyK7j1rNww==

As you can see, the MD5 of the content isn&#39;t the same as the MD5
part of the `X-Goog-Hash` header. (In my client library I&#39;m using the crc32c
hash, but that shows the same behavior.)

This isn&#39;t a bug in `HttpClientHandler` - it&#39;s expected, but a pain
when I want to validate the hash. Basically, I need to at the
content before *and* after decompression. And I can&#39;t find any way
of doing that.

To clarify my requirements somewhat, I know how to prevent the decompression in `HttpClient` and instead decompress afterwards when reading from the stream - but I need to be able to do this without changing any the code that uses the resulting `HttpResponseMessage` from the `HttpClient`. (There&#39;s a lot of code that deals with responses, and I want to only make the change in one central place.)

I have a plan, which I&#39;ve prototyped and which works as far as I&#39;ve
found so far, but is a bit ugly. It involves creating a three-layer
handler:

- `HttpClientHandler` with automatic decompression disabled.
- A new handler which replaces the content stream with a new `Stream` subclass 
  which delegates to the original content stream, but hashes the data as it&#39;s read.
- A decompression-only handler, based on the Microsoft [`DecompressionHandler`][2] code.
  
While this works, it has disadvantages of:

- Open source licensing: checking exactly what I need to do in order
  to create a new file in my repo based on the MIT-licensed
  Microsoft code
- Effectively forking the MS code, which means I should probably
  make a regular check to see if any bugs have been found in it
- The Microsoft code uses internal members of the assembly, so it
  doesn&#39;t port as cleanly as it might.
  
If Microsoft made `DecompressionHandler` public, that would help a
lot - but that&#39;s likely to be in a longer timeframe than I need.

What I&#39;m looking for is an alternative approach if possible -
something I&#39;ve missed that lets me get at the content before
decompression. I don&#39;t want to reinvent `HttpClient` - the response
is often chunked for example, and I don&#39;t want to have to get into
that side of things. It&#39;s a pretty specific interception point that
I&#39;m looking for.

  [1]: https://googlecloudplatform.github.io/google-cloud-dotnet/docs/Google.Cloud.Storage.V1/index.html
  [2]: https://github.com/dotnet/corefx/blob/master/src/System.Net.Http/src/System/Net/Http/Managed/DecompressionHandler.cs


Is it possible to access the compressed data before decompression in HttpClient?

I&#39;m using [iTextSharp][1] to read the text from a PDF file. However, there are times I cannot extract text, because the PDF file is only containing images. I download the same PDF files everyday, and I want to see if the PDF has been modified. If the text and modification date cannot be obtained, is a [MD5][2] checksum the most reliable way to tell if the file has changed? 

If it is, some code samples would be appreciated, because I don&#39;t have much experience with cryptography.

  [1]: https://en.wikipedia.org/wiki/IText
  [2]: http://en.wikipedia.org/wiki/MD5


Calculate MD5 checksum for a file

I am using code `$enrypt=md5($pass)` and inserting `$encrypt` to database. I want to find out a way to decrypt them. I tried using a  decrypting software but it says the hash should be of exactly 16 bytes. is there any way to decrypt it or to make it a 16 byte md5 hash?

My hash looks like this: `c4ca4238a0b923820dcc`

encrypt and decrypt md5

In my app I have a requirement to generate an MD5 checksum for a file. Could you please tell me if there is any way in which this can be achieved?

Thank you.

How to generate an MD5 checksum for a file in Android?

I&#39;m aware that MD5 has had some collisions but this is more of a high-level question about hashing functions. 

If MD5 hashes any arbitrary string into a 32-digit hex value, then according to the [Pigeonhole Principle][1] surely this can not be unique, as there are more unique arbitrary strings than there are unique 32-digit hex values.


  [1]: https://en.wikipedia.org/wiki/Pigeonhole_principle &quot;Pigeonhole Principle&quot;

How are hash functions like MD5 unique?

My understanding is that SSL combines an encryption algorithm (like AES, DES, etc.) with a key exchange method (like Diffie-Hellman) to provide secure encryption and identification services between two endpoints on an un-secure network (like the Internet).

My understanding is that SASL is an MD5/Kerberos protocol that pretty much does the same thing.

So my question: what are the pros/cons to choosing both and what scenarios make either more preferable? Basically, I&#39;m looking for some guidelines to follow when choosing SSL or to go with SASL instead. Thanks in advance!

Security &amp; Authentication: SSL vs SASL

What is the best way of generating a hash for the purpose of storing a session? I am looking for a lightweight, portable solution.

What is the best way to create a random hash/string?

As many will know, one-way encryption is a handy way to encrypt user passwords in databases. That way, even the administrator of the database cannot know a user&#39;s password, but will have to take a password guess, encrypt that with the same algorithm and then compare the result with the encrypted password in the database. This means that the process of figuring out the password requires massive amounts of guesses and a lot of processing power.

Seeing that computers just keep getting faster and that mathematicians are still developing these algorithms, I&#39;m wondering which one is the most secure considering modern computing power and encryption techniques.

I&#39;ve been using MD5 almost exclusively for years now, and I&#39;m wondering if there&#39;s something more I should be doing. Should I be contemplating a different algorithm?

Another related question: How long should a field typically be for such an encrypted password? I must admit that I know virtually nothing about encryption, but I&#39;m assuming that an MD5 hash (as an example) can be longer and would presumably take more processing power to crack. Or does the length of the field not matter at all, provided that the encrypted password fits in it in the first place?

What is currently the most secure one-way encryption algorithm?

In the [Flickr API docs][1], you need to find the MD5 sum of a string to generate the `[api_sig]` value.

How does one go about generating an MD5 sum from a string? 

Flickr&#39;s example:

string: `000005fab4534d05api_key9a0554259914a86fb9e7eb014e4e5d52permswrite`

MD5 sum: `a02506b31c1cd46c2e0b6380fb94eb3d`


  [1]: http://www.flickr.com/services/api/auth.howto.web.html

How to get MD5 sum of a string using python?

Up to what string length is it possible to use MD5 as a hash without having to worry about the possibility of a collision?

This would presumably be calculated by generating an MD5 hash for every possible string in a particular character set, in increasing length, until a hash appears for a second time (a collision). The maximum possible length of a string without a collision would then be one character less than the longest of the colliding pair.

Has this already been tested for MD5, SHA1, etc?

What&#39;s the shortest pair of strings that causes an MD5 collision?

I&#39;m building a system which needs to be able to find if **blobs of bytes have been updated**. 
Rather than storing the whole blob (they can be up to 5MBs), I&#39;m thinking I should compute a checksum of it, store this and compute the same checksum a little bit later, to see whether the blob has been updated.

The goal is to minimize the following (in that order) :

 - size of the checksum 
 - time to compute 
 - likeliness of collisions (2 identical checksums happening even if the content has been modified).

It is acceptable for our system to have collision not more than 1/1,000,000. The concern is not security, but simply update/error detection, so rare collisions are ok. (Which is why I put it last in the things to minimize).

Also, we cannot modify the blobs of text ourselves.

Of course, `md5`, `crc` or `sha1` come to mind, and if I wanted a quick solution, I&#39;d go for it. However, more than a quick solution, I&#39;m looking for what could be *a comparison of different methods as well as the pros and cons*. 

All Md5 Solutions on Gang of Coders

Total of 51 Md5 Solutions