1. A circuit arrangement, in particular an integrated circuit, such as a mathematical coprocessor, for performing at least one operation, in particular at least one cryptographic calculation, characterized in that at least one, preferably two, prime numbers for key generation, in particular for R[ivest-]S[hamir-]A[dleman] key generation, are searched in compliance with at least one defined digital signature law, in particular with the German Digital Signature Law.