Automated contact list matching with improved privacy

A method for matching a first plurality of private data sets stored in a communication client device with a second plurality of data sets stored on a server communication system, comprising the steps of:

• a) the communication client device processing or computing a predetermined hash value length s representing a number of bits of a cryptographic hash value of a unique portion of each of the private data sets to be transmitted between the communication client device and server communication system,
• b) the client device shortening the cryptographic hash value for each of the private data sets to a predetermined length s,
• c) the communication client device sending for each of the private data sets the shortened hash value to the server communication system, requesting the server communication system to match the private data sets with the second plurality of data sets stored on the server communication system,
• d) the communication client device receiving a hash value for each match, which hash value has been shortened to a plurality of a predetermined number of m bits by the server communication system,
• e) the communication client device matching the received m-shortened hash values to the data sets stored at the communication client device, thus revealing information for which private data sets stored both at the communication client device and at the server communication system the respective unique portion is identical.

A computer system, comprising:

• a memory and a processor for performing a method for matching a first plurality of private data sets stored in a communication client device with a second plurality of data sets stored on a server communication system, comprising the steps of:
• a) the server communication system computing a hash value length s representing a number of bits of a cryptographic hash value of a unique portion of each of the private data sets to be transmitted between the communication client device and the server communication system, and the server communication system communicating s to the communication client device,
• b) the server communication system receiving for each of the first plurality of private data sets a shortened hash value from the communication client device along with a request to match the private data sets with the second plurality of data sets stored on the server communication system,
• c) the server communication system checking if the length of the received shortened hash values actually equals s,
• d) if the length of the shortened hash values equals s, the server communication system matching each of the received shortened hash values to the second plurality of data sets stored on the server communication system, the server communication system finding the stored data sets having an identical shortened hash value,
• e) the server communication system enlisting each of the found stored data sets having the identical shortened hash value to a respective one of the received hash value,
• f) the server communication system shortening the found stored data sets having the identical shortened hash value to a predetermined length of m bits, and
• g) the server communication system sending for each of the received shortened hash values a list of m-bit shortened hash values to the communication client device.

A non-transitory computer-readable medium comprising a server computer program for execution in a server data processing system, implementable in a client-server network, for matching a first plurality of private data sets such as a private contact book stored in a communication client device with a second plurality of data sets such as a large contact data repository stored on a server communication system, comprising instructions stored thereon for causing a computer to perform a method for matching a first plurality of private data sets stored in a communication client device with a second plurality of data sets stored on a server communication system, comprising the steps of:

• a) the server communication system computing a hash value length s representing a number of bits of a cryptographic hash value of a unique portion of each of the private data sets to be transmitted between the communication client device and the server communication system, and the server communication system communicating s to the communication client device,
• b) the server communication system receiving for each of the first plurality of private data sets a shortened hash value from the communication client device along with a request to match the private data sets with the second plurality of data sets stored on the server communication system,
• c) the server communication system checking if the length of the received shortened hash values actually equals s,
• d) if the length of the shortened hash values equals s, the server communication system matching each of the received shortened hash values to the second plurality of data sets stored on the server communication system, the server communication system finding the stored data sets having an identical shortened hash value,
• e) the server communication system enlisting each of the found stored data sets having the identical shortened hash value to a respective one of the received hash value,
• f) the server communication system shortening the found stored data sets having the identical shortened hash value to a predetermined length of m bits, and
• g) the server communication system sending for each of the received shortened hash values a list of m-bit shortened hash values to the communication client device, when said computer program is executed on a processor on the computer.

A non-transitory computer-readable medium comprising a client computer program for execution in a client data processing system, implementable in a client-server network, for matching a first plurality of private data sets such as a private contact book stored in a communication client device with a second plurality of data sets such as a large contact data repository stored on a server communication system, having instructions stored thereon for executing a method for matching a first plurality of private data sets stored in a communication client device with a second plurality of data sets stored on a server communication system, comprising the steps of:

• a) the communication client device processing or computing a predetermined hash value length s representing a number of bits of a cryptographic hash value of a unique portion of each of the private data sets to be transmitted between the communication client device and server communication system,
• b) the client device shortening the cryptographic hash value for each of the private data sets to a predetermined length s,
• c) the communication client device sending for each of the private data sets the shortened hash value to the server communication system, requesting the server communication system to match the private data sets with the second plurality of data sets stored on the server communication system,
• d) the communication client device receiving a hash value for each match, which hash value has been shortened to a plurality of a predetermined number of m bits by the server communication system,
• e) the communication client device matching the received m-shortened hash values to the data sets stored at the communication client device, thus revealing information for which private data sets stored both at the communication client device and at the server communication system the respective unique portion is identical, when said computer program is executed on a processor on a client computer.