IACR News item: 24 October 2013
Tolga Acar, Lan Nguyen, Greg Zaverucha
ePrint Report
This note describes a Diffie-Hellman oracle, constructed using standard Trusted Platform Module (TPM) signature APIs. The oracle allows one to compute the exponentiation of an arbitrary group element to a specified TPM-protected private key.
By employing the oracle, the security provided by a group of order p is reduced by log k bits, provided k oracle queries are made and p +/- 1 is divisible by k. The security reduction follows from a straightforward application of results from Brown and Gallant (IACR ePrint 2004/306) and Cheon (Eurocrypt 2006) on the strong Diffie-Hellman problem.
On a more positive note, the oracle may allow a wider range of cryptographic protocols to make use of the TPM.
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