MD5 is a hash function that is no longer considered secure from a cryptographic point of view. Therefore, it should only be used for backward compatibility.

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Does this guarantee a unique 32 bit Hash?

I came across some source code that loosely does the below in order to achieve a 32 bit hash. The input string is passed through MD5 to get 16 bytes Hash (as usual). Then the 16 bytes are split into ...
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406 views

Question about modifying the MD5 plain text to cause a collision

I was trying to understand MD5 and got stuck with this question, its from Michael sipser's book on Information security Principles and Practice, 2nd edition The MD5 collision in Problem 25 is said ...
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221 views

Creating colliding x509 certificates: Crafting RSA moduli step

I am trying to generate 2 x509 certificates with the same signature but different values in the common name field, based on md5 collisions, as it was specified in this paper (page 7). Now I have ...
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40 views

Will length-extension work if secret is not prefixed but appended to the data? [duplicate]

Possible Duplicate: Why is h(m||k) insecure? Length-extension allows to append any data to the message while not knowing the secret. Any length-extension explaination one the web considers ...
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1k views

Generate fixed length cipher text from arbitrary length plaintext

Using an encryption algorithm like AES, is it possible to generate a fixed length cipher text no matter how long the plain text becomes?
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1answer
172 views

Is it possible to demonstrate that md5(x) != x for any x?

I am looking for an easy to follow explanation, if possible, that demonstrates/proves the validity (or not!) of this assertion: for any X, md5(X) != X (being X any string of 32 hex characters)
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1answer
213 views

why hash(hash(str)) is bad?

Why do people say that using hash twice or more is bad? yes there is key derivation that do that job, but in a low bandwidth network countries, the solution i see is to use a simple hashing system on ...
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2answers
58 views

Collision probability of MD5 over different attacks

I am researching the collision probability of MD5 and various attacks against it. Can someone help me how to learn the least probability that there will be a collision in a specific attack on MD5? ...
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1answer
254 views

What does it mean when two encrypted files, encrypted with the same method but with different keys, when xor'd together, produce a repeating pattern?

Let's say I have fileA and fileB, both encrypted somehow, but in the same method with different keys. If I xor them together, they will make a repeating pattern of 32 bytes length. What does that ...
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1k views

Is Dropbox's hashing method cryptographically secure?

Dropbox uses CRC32 and md5 to create a checksum of each 4 mb "block" as part of the their compression/file system. I suspect that Dropbox uses an additional cryptographic hash to check if there's a ...
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863 views

Can md5 be used for encrypting data?

I know that md5 shouldn't be used for password hashing because of collisions and possibility of making dictionary attacks e.g. using rainbow tables. But what about ...
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1answer
80 views

Are there any valid, and person readable, checksums possible?

We've been trying to produce a valid, and pretty, MD5. Something that has repeating digits, or spells a word, or something. It's probably more difficult than spelling out the dictionary on a ...
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418 views

Finding partial pre-image of MD5 hash

I have the following requirement for hashing using MD5. H(A,B,C,X); Where values A,B & C are given. However X is not given. I would like to find out what value of X would give a hash beginning ...
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1answer
127 views

MD5 pre-fixing with an unkown postfix

Is the MD5 prefixing attack still valuable to an attacker if he doesn't know the postfix of the string? For instance, what if the following sanity check was being used: ...
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1answer
171 views

Creating unique keys with md5

The project I'm working on requires me to find a way to create a unique key based on data stored in a table. The table in question consists of x columns and y rows. In order to create the key I want ...
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1answer
42 views

Can I use HKDF to improve security of HMAC used with weak hash function?

I am writing a framework which encrypts/decrypts files (or streams, in general) with symmetric key using block cipher (for example, AES). To authenticate encrypted file, I use HMAC, which is ...
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1answer
167 views

Problem with testing MD5 collisions

I am trying to test MD5 collisions presented in “Collisions for Hash Functions MD4, MD5, HAVA” (PDF) by Xiaoyun Wang, Dengguo Feng, Xuejia Lai, Hongbo Yu; 2004. I wrote a PHP script to test it, but ...
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1answer
276 views

IPsec authentication and encryption lgorithms

I am looking for the implementation of IPsec security algorithms for both authentication and Encryption. Is there any open source implementation available for the same ? And if someone supposed to ...
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28 views

Determine safety of exercise hash functions

There have been several attacks against hash functions such as $h_{sha1}$ and $h_{md5}$. Professor A suggests a new function $h_{666}$ with an output length of 666 bits. Professor B suggests ...
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60 views

TCR hash functions from MD5

I'm reading Collision-Resistant Hashing: Towards Making UOWHFs Practical (pag. 10 and 11) and here say The most direct way to construct a TCR hash function is to key a function like MD5 or SHA-1. ...
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1answer
199 views

MD5 implementation

As a personal project, I want to implement MD5 on an FPGA, but I have some doubts about the specifics of the implementation. My first source of how the algorithm is implemented was the RFC 1321, where ...
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1answer
133 views

Collision attacks on digital signatures

After reading this document about MD5 collision attacks, I still don't understand how collisions can make digital signatures insecure. In the paper, the researchers created two files with the same ...
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1answer
2k views

Does ssl_rsa_with_rc4_128_md5 have known weaknesses?

My bank's website uses HTTPS with the cipher suite ssl_rsa_with_rc4_128_md5. What are the known weaknesses of this suite? Do they have a practical impact for ...
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70 views

Integrity compromised - HASH modified

As we are all aware that HASHing is user to verify integrity in cryptography. I have a query about hashing. Suppose a man in the middle attacker manipulates the data and creates new HASH (by running ...
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3answers
280 views

Should I use md5 for my new application?

MD5 is a very fast hash and its output is short and easy to store. Should I use it for my non-security-sensitive application? I don't think so, but I can't seem to convince anyone else that this is ...
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1answer
59 views

Will there always be 256 collisions for the output of the MD5 hashsum function for 17-byte inputs?

By my math, if you are inputting all possible 17 byte values, and the output is 16 bytes long, then there must always be 256 possible inputs that will result in each output hashsum. However, looking ...
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238 views

Cracking secret key of a MD5 hash?

I have a MD5 hash which is obtained by hashing certain strings appended by a pipe character ( | ). (I know the values of these) A secret key is added as a suffix to this (I don't know the secret key). ...
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1answer
182 views

Thoughts on secure hashing and the “mds” algorithm

Almost a decade ago Raymond Chen blogged [1] about the "hash reset attack" cautioning developers to record the content length in addition to the message digest. Recently I came up with a variation on ...
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1answer
77 views

MD5 update functions

In the hashlib module in python is a function called m.update() where m is a ...
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1answer
81 views

How can one generate pairs/triplets/…/n-ary MD5 collisions

Is there a way to generate n strings with the same MD5 hash?
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1answer
373 views

What is the relation between hash chaining and chosen prefix attack

I read that hash chaining can be used to prevent hash collisions, while the chosen prefix attack allows hash collisions for algorithms like MD5. How are they related? Does hash chaining prevent the ...
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1answer
73 views

Does MD5 hash have quasi commutative property? [duplicate]

I am implementing a one-way accumulator using MD5 hash, wondering wheather it has quasi commutative property or not.
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104 views

What can cause similar MD5 hashes

I have a set of MD5 hashes with huge similarities in the second half of the hash, (made up) examples: ...
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51 views

Recovering a constant salt for MD5 [duplicate]

I have STRING and MD5(STRING+SALT) for any infinitely many STRING's. Is their any way that I can recover the SALT itself? (SALT is constant) I actually know SALT, but this is an intellectual exercise. ...
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513 views

Padding of Original Message in MD5

what should I do if my original message is greater than 64 bits? what is the process of padding in MD5? As described in Internet Security: Cryptographic Principles, Algorithms and Protocols, page ...
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1answer
88 views

Should I remove these use cases of MD5/SHA1 from my program?

I have a web app (a register and login system) written already but i am now improving it. One of its design goals was high security. I have some use cases of md5 and sha1 in it and now i am in doubt ...