Efficient long-term validation of digital signaturesAnsper, A.; Buldas, Ahto; Roos, Meelis; Willemson, JanPublic Key Cryptography : 4th International Workshop on Practice and Theory in Public Key Cryptosystems : PKC 2001 : Cheju Island, Korea, February 13-15, 2001 : proceedings2001 / p. 13-15

Improving the availability of time-stamping servicesAnsper, A.; Buldas, Ahto; Saarepera, Märt; Willemson, JanInformation Security and Privacy : 6th Australian Conference : ACISP 2001 : Sydney, Australia, July 11-13, 2001 : proceedings2001 / p. 360-375