CODEWITHSUNDEEP
md5
Nathan
Nathan

Reputation: 1260

What are the chances of having 2 strings with the same md5 hash?

I read somewhere that md5 is not 100% secure. Hence, the question.

Upvotes: 1

Views: 3082

Answers (1)

Joe C.
Joe C.

Reputation: 1538

You seem to be asking 2 separate but related questions.

The probability of a random collision is highly dependent on the size of the data that you're working with; the more strings you're hashing, the more likely a collision is to occur. See the first table at Wikipedia: Birthday Attack for exact probabilities. MD5 uses 128 bits, so to achieve a 50% collision probability, you'll need 2.2E19 strings.

However, while random collisions are suitably rare for small data sets, MD5 has been shown to be completely insecure against intentional collisions. According to the Wikipedia article on MD5, a collision attack exists that can be run in seconds on a 2.6Ghz Pentium4 processor. For security, MD5 is completely broken, and has been considered so since 2005.

If you need to securely hash something, use one of the more modern hashing algorithms, such as SHA-2, SHA-3 (when it's development is finished), or Whirlpool.

Upvotes: 2

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