202 votes

How to approach replacing md5 for transporting Unity game data to a remote server

This approach is fundamentally flawed. Anything on the client side can and will be tampered with by players. It is the same problem which makes DRM untenable - the user owns the machine and all the ...
Polynomial's user avatar
  • 135k
107 votes
Accepted

Known strings to have the same MD5 hash, not colliding in real life?

... in which it clearly states that these two strings ... No. It clearly states "... two different sequences of 128 bytes ...". There is a huge difference in these statements. In the first ...
Steffen Ullrich's user avatar
96 votes
Accepted

Is it secure to use MD5 to verify the integrity of small files (less than 15kb)?

The size of the input is irrelevant. In fact, because of the birthday paradox, collisions are guaranteed as soon as the size of the message exceeds that of the hash. The best way to avoid collisions ...
forest's user avatar
  • 66.7k
92 votes
Accepted

Is bcrypt(strtolower(hex(md5(pass)))) ok for storing passwords?

As a password cracker, I encourage all of my targets to use this technique. 😉 This (understandably!) seems like a good idea, but it turns out that against real-world attacks, wrapping an unsalted ...
Royce Williams's user avatar
69 votes
Accepted

How long will it take to crack the passwords stolen in the Yahoo hack announced 14 Dec 2016?

Yes, they were likely able to crack many of the passwords in a short time. From the official Yahoo statement: For potentially affected accounts, the stolen user account information may have ...
Arminius's user avatar
  • 44.8k
59 votes
Accepted

Exploiting MD5 vulnerability in this PHP form?

Try sending a HEAD request. I'm assuming that with ascii.txt included, the output of the script is just over a nice number like 4096 bytes, a common output_buffering value. Once the script has ...
gabedwrds's user avatar
  • 665
46 votes
Accepted

Why would one need to encode an MD5 hash string? Is it unsafe to display unencoded?

Hash functions output binary data, usually as a byte array. This cannot be displayed correctly, therefore, you need encoding. Transmitting binary data can create problems, especially in protocols that ...
kelalaka's user avatar
  • 5,559
43 votes
Accepted

How can I prove this site has a huge security weakness?

The password format in the userpassword attribute looks like the standard format used by various unix services, such as the default system password service which stores hashed passwords in /etc/shadow....
Out of Band's user avatar
  • 9,273
40 votes

How to approach replacing md5 for transporting Unity game data to a remote server

There are three problems here: What you're trying to do is fundamentally misguided in several ways, as described in Polynomial's answer. If you insist on doing it anyway, then you're not even using ...
Nathaniel J. Smith's user avatar
40 votes
Accepted

Received "md5" in access logs

The attacker is trying to exploit Joomla component called com_s5clanroster which is vulnerable to SQL Injection. An SQL injection vulnerability has been reported in Joomla Com S5clanroster. ...
Mirsad's user avatar
  • 10.2k
39 votes

Known strings to have the same MD5 hash, not colliding in real life?

As pointed out in the other answers, the hexadecimal strings must be decoded to raw bytes first, then the raw bytes should be fed into the MD5 hash function. If you do this, both produce a hash of ...
mti2935's user avatar
  • 23.4k
37 votes

Is bcrypt(strtolower(hex(md5(pass)))) ok for storing passwords?

While Royce's answer is correct in that wrapped hashes are weaker than unwrapped pure bcrypt hashes, it must be noted that they are nevertheless significantly stronger than your current implementation ...
March Ho's user avatar
  • 1,705
37 votes

SHA & MD5 Collisions for shorter strings

Short answer: collisions don't matter for password verification. The length of the input is irrelevant. I understand that md5 and sha512, etc... are insecure because they can have collisions. No, ...
Gilles 'SO- stop being evil''s user avatar
28 votes

How can I prove this site has a huge security weakness?

This password hash seems to use the crypt() format (which, despite its name and what some documentations say, including that very man page, has absolutely nothing to do with encryption; it is hashing)....
Thomas Pornin's user avatar
27 votes

Exploiting MD5 vulnerability in this PHP form?

The security flaw isn't in MD5 in this case. And the idea isn't to get if (!isset($_POST['pass']) || md5($_POST['pass'])!='castle') to evaluate in favor of the hacker. The vulnerability appears when ...
Bacon Brad's user avatar
  • 3,392
27 votes
Accepted

How to approach replacing md5 for transporting Unity game data to a remote server

Edit: To clarify, I can't speak to the security of your approach, only the hash portion. There are some strong comments here discouraging your approach. (i.e. a good hash can be part of a secure ...
700 Software's user avatar
24 votes
Accepted

Convert SHA-256 to SHA-1 and MD5 - Increase bit length/entropy?

And it is longer than the input string, with 288bit instead of 256bit. So did we actually increased the entropy? No, you did not increase the entropy. In this context, "entropy" basically refers to ...
user's user avatar
  • 7,795
23 votes
Accepted

Client side password hashing with static salt - did I find a breach?

It depends. There is not enough information in your question to give specific answers, and probably without knowing the server side, it will be hard to evaluate. Isn't this a breach? I would not call ...
phisch's user avatar
  • 1,315
22 votes

How can I prove this site has a huge security weakness?

Stop. Go no further. Do no more testing, demonstration, etc. until you have been explicitly asked to do so in writing, and even then beg off and suggest that there are many more qualified people than ...
ivanivan's user avatar
  • 339
21 votes

How long will it take to crack the passwords stolen in the Yahoo hack announced 14 Dec 2016?

(Summary is in the last paragraph.) How long will it take to crack 1 password? Is the time to crack 1 billion, just 1e9 * t? Imagine I have this hashing algorithm: function hash(password): ...
Luc's user avatar
  • 32.9k
20 votes

Known strings to have the same MD5 hash, not colliding in real life?

Those are byte values not strings. Use https://cryptii.com/pipes/md5-hash and change input to bytes. Both byte arrays produce equal hash 79054025255fb1a26e4bc422aef54eb4.
roscoe's user avatar
  • 311
19 votes

I have an MD5 encrypted link. How do I decrypt?

It's not MD5 (which is a message digest algorithm, not an encryption algorithm), and it's not even base 64. It's just ASCII encoded as hex. It contains http://imgur.com/EUJCsGB which is a link to ...
John Deters's user avatar
  • 34.2k
17 votes

Exploiting MD5 vulnerability in this PHP form?

I've seen a similar challenge somewhere. Try to send something like 'QNKCDZO' as input. md5('QNKCDZO') is '0e830400451993494058024219903391' (note the 0e prefix in the hash indicating scientific ...
Younis Bensalah's user avatar
17 votes
Accepted

MD5 Preimage Vulnerability in 2017

MD5 should be considered completely compromised for password use, and has been "deprecated" for passwords for a long time. It doesn't even have to involve preimage attacks or explicit vulnerabilities....
Conor Mancone's user avatar
16 votes
Accepted

Which hashing algorithm shoud I use for a safe file checksum?

Choice of hash algorithm Use SHA-256 or SHA-512: either of the two “main” members of the SHA-2 family. SHA-2 is the successor of SHA-1 and is considered secure. It's the hash to choose unless you ...
Gilles 'SO- stop being evil''s user avatar
15 votes

Does re-hashing a part of the password hash increase security?

Only the code would know how many characters were being used to re-encrypt the first hash code. And this is where the problem is. Right at the start, only one with access to the code knows this. But ...
S.L. Barth is on codidact.com's user avatar
15 votes
Accepted

Why is MD5 considered a vulnerable algorithm?

I know that MD5 is the most vulnerable hashing algorithm Well technically (we are technical around here) there are worse algorithms than MD5. and particularly vulnerable to Collisions Yes, folks ...
700 Software's user avatar
15 votes

Why would one need to encode an MD5 hash string? Is it unsafe to display unencoded?

What you see as the MD5 hash is the hex encoded version of it. The hash itself is binary, but we usually don't like to see binary data on screen. Another way to display the hash is using Base64, so ...
ThoriumBR's user avatar
  • 54.1k
14 votes

How likely is a collision using MD5 compared to SHA256 (for checking file integrity)?

There seems to be some confusion about the capabilities of a collision attack. Two of the properties a cryptographic hash must have are collision resistance and preimage resistance. If a hash is ...
AndrolGenhald's user avatar

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