Security Analysis of RSA-BSSA

Abstract

In a blind signature scheme, a user can obtain a digital signature on a message of her choice without revealing anything about the message or the resulting signature to the signer. Blind signature schemes have recently found applications for privacy-preserving web browsing and ad ecosystems, and as such, are ripe for standardization. In this paper, we show that the recent proposed standard of Denis, Jacobs and Wood [16, 17] constitutes a strongly one-more-unforgeable blind signature scheme in the random-oracle model under the one-more-RSA assumption. Further, we show that the blind version of RSA-FDH proposed and analyzed by Bellare, Namprempre, Pointcheval and Semanko [6] does not satisfy blindness when the public key is chosen maliciously, but satisfies a weaker notion of a blind token.