ENCRYPTION METHOD AND DEVICE USING AN RSA-TYPE CRYPTOSYSTEM

摘要

The invention relates to an encryption method and device using an RSA-type cryptosystem. More specifically, the invention relates to a method of selecting the private key of the RSA cryptosystem, once the encryption exponent e has been fixed, which, in addition to being secure against factoring attacks, is novel in that it is invincible to attacks based on the length of the W-B-D-type decryption exponents. The inventive private key selection method not only guarantees that e has the desired value and that the size of the decryption exponent d resists W-B-D-type attacks, but also that the size thereof is much greater than that recommended in order to prevent such attacks. In fact, the number of d bits is the maximum possible (the same as the number of bits of modulus n) or, at most, one bit less than the maximum.