Hash Range Queries

For simple, privacy-preserving data-sharing.

Transcript

1. Hash Range Queries
   For simple, privacy-preserving data-sharing
   

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2. https://blog.cloudflare.com/validating-leaked-passwords-with-k-anonymity/

   https://www.troyhunt.com/ive-just-launched-pwned-passwords-version-2/
   Not my original idea
   

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3. https://api.pwnedpasswords.com/pwnedpassword/password
   A request for a single password reveals who is
   interested in this password.
   Maybe not that interesting for a widely-used value
   …
   

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4. https://api.pwnedpasswords.com/pwnedpassword/p1nkyp13
   But how many people would use their favorite my
   little pony character with vowels replaced with
   numbers?
   

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5. Do you trust the person
   operating the service?
   • Are they doing something else with the data?
   
   • Are they securing the data?
   

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7. How can a client get a single
   record from a server without
   revealing the record identifier
   to the server?
   

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8. The Easiest Way:
   Hashed Identifiers
   

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11. But
    rainbow tables exist
    

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13. The Hard Way:
    Private Set Intersection
    

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16. The Middle Way:
    k-Anonymity
    

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17. https://en.wikipedia.org/wiki/K-anonymity
    Every record is unique
    

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18. https://en.wikipedia.org/wiki/K-anonymity
    k-Anonymity: 2
    for any combination of Age + Gender + State found in any row of the table
    there are always at least 2 rows with those exact attributes
    Suppression Suppression
    Generalization
    

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19. https://blog.cloudflare.com/validating-leaked-passwords-with-k-anonymity/
    By using this property, we are able to seperate hashes
    into anonymized "buckets".
    

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20. https://blog.cloudflare.com/validating-leaked-passwords-with-k-anonymity/
    A client is able to anonymize the user-supplied
    hash …
    

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21. https://blog.cloudflare.com/validating-leaked-passwords-with-k-anonymity/
    … and then download all hashes in the same
    anonymized "bucket" as that hash …
    {
    

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22. https://blog.cloudflare.com/validating-leaked-passwords-with-k-anonymity/
    {
    5baa61e4c9b93f3f0682250b6cf8331b7ee68fd8
    5baa61f4c0b12f0a6691121c7de9420c8ff12c1f
    5baa61aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
    5baa61bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
    5baa61cccccccccccccccccccccccccccccccccc
    5baa61e4c9b93f3f0682250b6cf8331b7ee68fd8
    5baa61f4c0b12f0a6691121c7de9420c8ff12c1f
    5baa61aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
    5baa61bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
    5baa61cccccccccccccccccccccccccccccccccc
    … then do an offline check to see if the user-
    supplied hash is in that breached bucket.
    

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