Questions tagged [md5]

a cryptographic hash function with a 128-bit (16-byte) output, now deprecated

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96
votes
7answers
122k views

Is MD5 considered insecure?

After all these articles circulating online about md5 exploits, I am considering switching to another hash algorithm. As far as I know it's always been the algorithm of choice among numerous DBAs. Is ...
78
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3answers
22k views

How can I create a password that says "SALT ME!" when hashed?

How can I create a password, which when directly hashed (without any salt) with md5 will return a string containing the 8 characters "SALT ME!". The hope is that a naive developer browsing through his ...
77
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4answers
21k views

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

Apparently Yahoo was hacked yet again with up to a billion user accounts being compromised. The article says Yahoo uses MD5 for password hashing. Are the hackers likely to be able to crack the ...
73
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4answers
185k views

Is SHA1 better than MD5 only because it generates a hash of 160 bits?

It is well known that SHA1 is recommended more than MD5 for hashing since MD5 is practically broken as lot of collisions have been found. With the birthday attack, it is possible to get a collision ...
64
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8answers
52k views

Why do people still use/recommend MD5 if it has been proven weak since 1996?

It's still a commonly recommended way of hashing passwords, even if its insecurity had been proven in 1996: Therefore we suggest that in the future MD5 should no longer be implemented in applications ...
56
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5answers
15k views

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

I know that collision for MD5 has been documented since the 90s and that digital certificates based off of MD5 has been demonstrated to be completely compromised back in 2010 but how effective is MD5 ...
56
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4answers
37k views

Why are MD5 and SHA-1 still used for checksums and certificates if they are called broken?

I was just reading about SSL/TLS stuff, and according to this site (which is rated as A by Qualys SSL Labs), MD5 is totally broken, and SHA-1 is cryptographically weak since 2005. And yet, I noticed ...
50
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4answers
14k views

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

TL;DR I am working on a gaming system that uses UnityScript and C# on the client and PHP on the server. A MD5 hash of the data plus a shared secret is used to check that the data has not been ...
46
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3answers
7k views

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

I have a large database where passwords are stored as strtolower(hex(md5(pass))) (which is a bad way to store passwords, prone to rainbow tables, cheap to dictionary attack, no salt, etc.), and I'm ...
42
votes
7answers
13k views

Exploiting MD5 vulnerability in this PHP form?

I've been practicing in security-related topics and I came upon this problem which I don't understand at all. You receive a form with one input named pass, and this is the code you need to bypass: &...
37
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5answers
11k views

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

Disclaimer: I'm a computer programmer, not a security analyst or anything to do with security. I have zero experience in the world of cryptography, so bear with me please. Situation: I was given the ...
34
votes
4answers
5k views

Does every hash value have an inverse value?

There are many different hash functions, md5, sha, and others. They take a value V and produce a H via transformation Function(V) = H, where Function is md5, sha, etc. My question is: Does every hash ...
30
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3answers
6k views

MD5 collision attacks: are they relevant in password hashing?

DISCLAIMER: This is not an endorsement of MD5 as a password hashing function. I know about parallelization, GPUs, and dedicated password hashing functions like bcrypt and scrypt. With that out of the ...
26
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3answers
7k views

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

I was reading this article about MD5 hash collisions in which it clearly states that these two strings (differences marked with ^): ...
26
votes
2answers
3k views

How can the content of a file refer to its own MD5?

So I just saw this picture on Imgur: http://imgur.com/gxRCrCM The intriguing thing about it is that the picture refers to an old Daft Punk song named "Face 2 Face". The image's MD5 is ...
25
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6answers
12k views

Why does some popular software still use md5?

Nowadays no one dares to defend md5 for any use, and of course they should not! However, much popular software still uses md5 in applications such as password hashing (although it's not simple/plain ...
25
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4answers
9k views

Is Postgres password-based authentication secure?

According to Postgres's documentation, Postgres's password authentication method uses MD5 hashing to secure the password: The password-based authentication methods are md5 and password. These ...
24
votes
2answers
15k views

Truncating the output of SHA256 to 128 bits

Suppose we need/prefer 128 bit hash output, for example to generate a 128 bit encryption key or, in other applications (e.g. file integrity verification), to consume less storage space. I don't know ...
23
votes
1answer
5k views

Received "md5" in access logs

In our Apache server we have received around 200 HTTP GET requests from the same IP and a common string in each request is "md5", e.g. index.php?option=com_s5clanroster&view=s5clanroster&...
21
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6answers
31k views

Reversible Hash Function?

Is there any reversible hash function? The hash function like SHA and MD5 are not reversible. I would like to know if there exist some reversible hash functions?
16
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2answers
42k views

How weak is MD5 as a password hashing function ?

A professor told us today, that MD5 is weak. I understand his chain of thought but pointed out, that IMHO MD5 is a good way to go if you would use a long (even really long) dynamic salts and static ...
15
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2answers
8k views

Difference between OS X md5 and gnu md5sum

I have installed the "md5sum" utility on my Mac and there was also a "md5" binary pre-installed in /sbin. My problem and question is this: "Isn't MD5 a standard algorithm?" Because I get different ...
14
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2answers
1k views

Password Salts and Randomness

Alright, so I understand that users are the kind of beasts who like to use one password and make it short and easy to remember (like "doggies"). If I understand correctly, that's one reason we use ...
14
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2answers
11k views

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

For my work I'll need to provide my customer a specific file which will be the result of the work I have done for them. To protect the integrity of the work I have done and to guarantee it has never ...
13
votes
4answers
15k views

Using MD5 for file integrity checks?

General Always check the MD5 hashes of the .NET Framework assemblies to prevent the possibility of rootkits in the framework. Altered assemblies are possible and simple to produce. Checking the ...
13
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3answers
17k views

How exactly is MD5 vulnerable to collission attacks?

I've often read that MD5 (among other hashing algorithms) is vulnerable to collisions attacks. I understand the collision part: there exist two (or more) inputs such that MD5 will generate the same ...
11
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5answers
6k views

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

I was reading this article which talks about a design to shorten URLs, and in the design section, it says that the given URL can be hashed using a hashing algorithm such as MD5, and then be encoded ...
11
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2answers
4k views

MD5 Preimage Vulnerability in 2017

I've recently discovered that one of our (strictly internal facing - no external risk unless other systems are completely compromised) platforms is storing passwords by salting and then MD5 hashing ...
10
votes
2answers
57k views

If hashing is one way, why can we decrypt MD5 hashes?

I have read some times that hashing is a one way function, that is you can make the hash of a message, but you can't recover the original message from the hash, just check its integrity. However, if ...
10
votes
3answers
19k views

Why do most hashing functions produce hashes that have characters a-f 0-9?

This is something I never understood about hashing functions. I know that algorithms like whirlpool and blowfish both produce outputs that don't follow this pattern, but why is it that most do? Is ...
10
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2answers
1k views

Is there any recommended approach for "upgrading" MD5 hashes to something secure? [duplicate]

I'm currently dealing with a couple of user accounts containing MD5 hashed passwords. These accounts got migrated from an old system into our current system which uses PBKDF2 for password hashing. I ...
10
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2answers
3k views

Migrating password db off MD5 by chaining MD5 and Bcrypt?

I have a legacy system currently storing unsalted MD5 passwords. Unfortunately, some other controls are not in place (like the ability to expire passwords) and I'm trying to upgrade my algorithm to ...
10
votes
3answers
10k views

What does GUID have, that a Whirlpool, MD5 or SHA-2 hash don't?

I'm trying to understand the use of GUID and what has always left me wondering is what's so special about them that I should consider using them instead of rolling my own type of unique ID. In other ...
10
votes
1answer
3k views

Checksums do not match when I download file over http

Just for the test I did the following: Downloaded a page from Wikipedia via wget on remote server and named the file test.dat. Then I executed md5sum. I download the file via HTTP and check it back ...
9
votes
4answers
4k views

SHA & MD5 Collisions for shorter strings

This is not for passwords. I understand that MD5 and SHA-512, etc... are insecure because they can have collisions. However, is it still possible to have a collision if the string length is less than ...
9
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3answers
3k views

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

I downloaded a software that has a login interface. It's a $100 a month subscription software. I disassembled the software and found that passwords are being sent by combining them with a hard coded &...
9
votes
7answers
7k views

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

Many sites these days offer MD5 and SHA256 hashes to check the integrity of downloaded files or archives. I wonder how much safer is the use of the SHA256 hashes for integrity checks? Note: Consider ...
9
votes
1answer
3k views

Does bcrypt on top of md5 reduce its security?

A GitHub project I recently checked has a flawed security as they're using an unsalted md5() to hash the passwords. I opened a bug and they acknowledged it. However, the transition from md5() to ...
8
votes
2answers
23k views

Why is MD5 considered a vulnerable algorithm?

I know that MD5 is the most vulnerable hashing algorithm, and particularly vulnerable to Collisions. But the collision vulnerability is not very risky and somebody might use that as an advantage, but ...
8
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3answers
1k views

Is Using MD5 Sufficient Reason to Reject This Payment Processor?

I'm evaluating a credit card processor[1], and I noticed they are using MD5 as part of a salted hash algorithm to protect a secret key. Since I know MD5 is generally considered broken, this feels like ...
8
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2answers
4k views

Does the md5 (or any hash for that matter) of a string include the null terminator?

Does the md5 (or any hash for that matter) of a string include the null terminator in its calculations? That is does the hash of a string equal the hash of the sequence of bytes that represents the ...
8
votes
3answers
4k views

NTLMv2 resistance to bruteforcing

I have a question regarding NTLMv2 resistance to password bruteforcing. I know that some modern graphic processors (like Radeon 6990) are able to calculate billions hashes per second and crack NTLM ...
7
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3answers
63k views

Why does MD5 hash starts from $1$ and SHA-512 from $6$? Isn't it weakness in itself? [duplicate]

I have moved this question from stackoverflow to this place. I know it may be a question about 'opinion' but I am not looking for a private opinion but a source of the final decision to keep it this ...
7
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2answers
10k views

Rounds of MD5 and SHA512 Hashing Algorithms

What is the exact number of rounds employed by the MD5 and SHA512 hashing algorithms? According to various sources, the SHA512 hashing algorithm employs a total of 80 rounds (http://en.wikipedia.org/...
7
votes
3answers
21k views

Client-side hashing of password before sending it from login form [duplicate]

I have just realized, that my web application is sending unencrypted passwords from login form. It's just like that -- I've analysed, that string sent by user from login form is hashed with MD5 (which ...
7
votes
1answer
16k views

The brute-force resistence of bcrypt versus MD5 for password hashing?

Can anyone give me an idea? Assume the salt(s) is/are known. For example, if I have a $k$-character long password that is hashed in MD5 versus bcrypt, is there a way to estimate how much more time it ...
7
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4answers
25k views

Is salted MD5 or salted SHA considered secure?

Is using something like bcrypt or scrypt necessary? The hashes are so much longer to store in a database. Can one get away with using salted MD5 or SHA and still be secure?
7
votes
3answers
14k views

Why is it necessary to match the checksum of a download with another file provided by the same server? [duplicate]

Possible Duplicate: Does hashing a file from an unsigned website give a false sense of security? On many servers providing files for download, there is a file on which checksums are provided for ...
7
votes
1answer
1k views

Is MD5 hashing possible by divide and conquer algorithm

I would like to compute the MD5 hash of a file The file is uploaded to my webserver by my clients The file is uploaded in pieces (called chunks) The client also sends the md5 hash of the file so that ...
7
votes
2answers
6k views

openssl enc uses md5 to hash the password and the salt

Wikipedia states that md5's collision resistance is 2^18 (https://en.wikipedia.org/wiki/MD5). I just found out that openssl enc uses md5 to hash the password and the salt. Let's assume that I want ...

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