<P> The RSA problem is defined as the task of taking eth roots modulo a composite n: recovering a value m such that c ≡ m (mod n), where (n, e) is an RSA public key and c is an RSA ciphertext . Currently the most promising approach to solving the RSA problem is to factor the modulus n . With the ability to recover prime factors, an attacker can compute the secret exponent d from a public key (n, e), then decrypt c using the standard procedure . To accomplish this, an attacker factors n into p and q, and computes lcm (p − 1, q − 1) which allows the determination of d from e . No polynomial - time method for factoring large integers on a classical computer has yet been found, but it has not been proven that none exists . See integer factorization for a discussion of this problem . </P> <P> Multiple polynomial quadratic sieve (MPQS) can be used to factor the public modulus n . The time taken to factor 128 - bit and 256 - bit n on a desktop computer (Processor: Intel Dual - Core i7 - 4500U 1.80 GHz) are respectively 2 seconds and 35 minutes . </P> <Table> <Tr> <Th> Bits </Th> <Th> Time </Th> </Tr> <Tr> <Td> 128 </Td> <Td> Less than 2 seconds </Td> </Tr> <Tr> <Td> 192 </Td> <Td> 16 seconds </Td> </Tr> <Tr> <Td> 256 </Td> <Td> 35 minutes </Td> </Tr> <Tr> <Td> 260 </Td> <Td> 1 hour </Td> </Tr> </Table> <Tr> <Th> Bits </Th> <Th> Time </Th> </Tr>

Which of the following are characteristics of rsa a public key algorithm