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TrustTester: Secure validation of personal data

Validating information without actually providing any data – that is value of TrustTester. TrustTester combines a patented algorithm with a system of agreements that together enable organisations to validate the correctness of the information provided by the consumer in an online process. This means that organisations have a more efficient control process and consumers maintain their privacy.

The consumer looking to get a mortgage must prove that he earns enough. A company intending to employ somebody requests an attestation of good behaviour. A student wanting cheap health Insurance has to prove he is enrolled at an institution of higher education. On the one hand, this is information organisations want to have. On the other hand, it is information that people prefer to keep to themselves.

Signatures and copies

In all kinds of online processes reliable information is required. If a bank wants to find out whether a consumer earns enough, it may not ask the employer directly. The Personal Data Protection Act stipulates that such requests are always made via the consumer. However, since the consumer may commit fraud, the information provided loses its credibility. The consequence of this is that the bank has to employ its experts in a time-consuming and expensive process of collecting signatures and copies.

Digital stamp

But, in fact, it is not about the information itself. Organisations only want to find out whether it is correct or not. The bank is not so much interested in finding out exactly how much the consumer earns but whether it is enough for the required mortgage. A simple and definitive ‘yes’ is better than a salary slip whose credibility has to be checked again. TrustTester makes this possible. TrustTester does not provide data but validates the consumer’s claim that he has a specific income. It validates the claim with a ‘digital stamp’ that the recipient – such as the bank – can trust.

Validate information without providing actual data

Homomorphic encryption

In practice, TrustTester is a bit like iDEAL. After the consumer has filled in his income on the bank’s website, a screen appears with the request to validate the amount. The consumer selects the source, such as the Employees Insurance Agency where his income is known, and logs in using his DigiD. TrustTester then ensures that the income filled in by the consumer and the income known in the database of the Employees Insurance Agency are homomorphically encrypted. Then a ‘secure data comparing protocol’ starts whereby the claim and actual income in the encrypted domain are compared until one bit remains on each side. Only the consumer is able to see what the outcome of the validation is on the basis of both bits. If he authorises the result to be shared, then the bank also receives proof that the claim is correct.


In January TNO is organising an experiment with TrustTester in which consumers will validate several attributes that play a role in a mortgage, like income level, having a lease car and a permanent employment contract. Other aspects include user-friendliness and conformity with existing law and legislation. If the experiment is successful, TrustTester will become available as an operational service in 2017. 

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