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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Is there any practical attack to create a printable chosen prefix MD5 collision?

I would like to create two ASCII text messages with the same MD5. Is this possible? If not, is there a similar but less strict attack that could work? Or to rephrase my last question: what are the ...
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1answer
27 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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24 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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3answers
189 views

Practical Uses for Timing Attacks on Hash Comparisons (e.g. MD5)?

Consider the following code snippet: ...
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2answers
282 views

Is HMAC-MD5 still secure for commitment or other common uses?

MD5 collisions have been out for some time. In spite of this, HMAC-MD5 is still secure for authenticating data1. This illustrates a strength of the HMAC construction, it does not require that the hash ...
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2answers
67 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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1answer
134 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
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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78 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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101 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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1answer
119 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
68 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 ...
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1answer
148 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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717 views

Why are the outputs of the md5sum tool and Crypto++'s MD5 different?

Could you please tell me what is the difference of coreutils' md5sum and sha*sum tools (...
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161 views

How were shift amount constants in MD5 found?

The md5 specification gives a series of 4 rounds to execute over a 16-word block. Each round has a repeating sequence of 4 shift amounts (s in ...
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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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1answer
67 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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1answer
214 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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1answer
198 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
72 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
163 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
397 views

How does MD5 process text which is shorter than 512 bits

MD5 processes a 512-bit block and produces a 128-bit (16 byte) message digest often expressed as 32-digit hexadecimal value For example if I hash the word "how" using MD5 , I get the following hash ...
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3answers
209 views

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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1answer
77 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
14k views

How is SHA1 different from MD5?

On the surface, SHA1 and MD5 look pretty similar. Their diagrams include chunks of bits, bit rotation, xor and special functions. Their implementations are roughly the same length (at least the ones ...
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1answer
1k views

Probability that two different files can have same MD5 hash for both an unencrypted and encrypted version (AES256, same key between files)

This math is way over my head, and don't even know if it can be done, but here are the assumptions: Take unencrypted File [Fu] of variable length, but assume 100KB as an example. Let File [Fe] be ...
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1answer
66 views

Calculating IHVs from known message and hash output

Here is a somewhat silly and atypical problem I am currently facing. Usually, when it comes to hashes, one is bothered with finding collisions and preimages. My problem is, I need to find the IHV used ...
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148 views

Is a collision attack possible on MD5 if message is known partially

Is it possible to find $m'$ such that $\operatorname{MD5}(m'||m_1)=\operatorname{MD5}(m_1||m_2)$ if I know $m_2$ and $\operatorname{MD5}(m_1||m_2)$? Is this a collision or a preimage attack? Also in ...
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3k views

What is the MD5 collision with the smallest input values?

I am interested in MD5 collisions for small input messages. The collision examples given at http://www.mscs.dal.ca/~selinger/md5collision/ show two different strings, where only a tiny amount of data ...
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1answer
189 views

Will hashing over and over eventually give the same hash?

There are many cases in maths where doing the same thing over and over again will bring you closer to a value. Derivation of polynomials is the striking example: no matter what you start with, you end ...
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1answer
243 views

Are the MD5 constants an S-Box?

I noticed that several hash algorithms, in this case MD5, defines some constants. MD5 defines 64 constant values (the shift count per round) which also gets expand (via sine) to a summand for a ...
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1answer
243 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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1answer
175 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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255 views

distribution for a subset of md5

I need to uniquely assign a 32 bit integer to a collection of human readable strings (i.e. they will not be generated with hash collision in mind). I don't expect more than a few thousand strings. I ...
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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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1answer
509 views

Is MD5 second-preimage resistant when used only on FIXED length messages?

I fully realize that MD5 should not be used in any new project, but in my particular situation I have severe CPU performance issues, so MD5 is convenient. I have read a lot about MD5 security for this ...
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2answers
2k views

Strength of MD5 in finding duplicate files

Why are there a lot of duplicate file finder applications which are using MD5 Algorithm? What is the strength of MD5 in terms of searching duplicate files in hard disk or flash driver or any other ...
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57 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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106 views

MD5 theoretical question

Ok, so this is a very possible stupid question, but one of those things that has sat at the back of my mind for a while. We all know that MD5 has issues, and these have been known for about a decade. ...
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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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390 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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1answer
117 views

md5sum collision question

I've been reading the wikipedia page, trying to get a better understanding of how to produce a collision. http://en.wikipedia.org/wiki/MD5#Collision_vulnerabilities The wikipedia page above states: ...
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1answer
357 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 ...
3
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1answer
172 views

salting with password hash to improve security?

Would something like the following improve security (against rainbow attacks, not brute force)? Assume that $P$ is a user-chosen password, and the objective is to obtain a hash $H$ for password ...
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1answer
166 views

Has it become easier to pre-compute tables after MD5 collisions?

Apparently it is not possible to compute all MD5 values from 0x00000000000000000000000000000000 to ...
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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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1answer
3k views

Is HMAC-MD5 considered secure for authenticating encrypted data?

I've read something to the effect that the HMAC construct is able to lessen the problem of collisions in the underlying hash. Does that mean that something like HMAC-MD5 still might be considered ...
2
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1answer
515 views

length extension attack on an MD5 hash of a text file of about 10K Bytes?

How much computing time on a typical desktop computer would it take to find a new length and new data to extend a text file of about 10K Bytes with a given MD5 hash?
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915 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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1k views

Using an MD5 hash as a password

Suppose Alice is using a password prompt that only accepts up to 32 characters for any particular password. Memorization of long strings of random characters is not one of Alice's strengths, so she ...