encryption - How to hash/encrypt a string to protect private information but still make the string comparable -

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given string how create unique identifier / hash string 1 can track occurence of string without logging original string.

for example url "www.mylittlesecret.com" should show "xyz123" (hascode string). url translates xyz123 xyz123 1 can't determine url.

sorry if wrong terms. happy read more "hashing" if provide me right keywords.

if use hash algorithm sha1 desired behavior. not able reconstruct url hash, can compare hashes , see if urls same or not.

but if wants find out urls have subjected dictionary attacks, users takes list of known web sites , sees if hashes matches. might watch out for.


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