For a public$-$key cryptosystem to achieve the same level of security of a private$-$key cryptosystem with a key length of $128$ bits, the public$-$key cryptosystem would require a key length

Question $25$ options:

A$)$

generally less than $128$ bits

B$)$

generally more than $128$ bits

C$)$

of $64$ bits

D$)$

also of $128$ bits