How we find security level in a cryptographic scheme?
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Answer: In cryptography, key size or key length is the number of bits in a key used by a cryptographic algorithm (such as a cipher).
Key length defines the upper-bound on an algorithm's security (i.e., a logarithmic measure of the fastest known attack against an algorithm, relative to the key length), since the security of all algorithms can be violated by brute force attacks. Ideally, key length would coincide with the lower-bound on an algorithm's security. Indeed, most symmetric-key algorithms are designed to have security equal to their key length. However, after design, a new attack might be discovered. For instance, Triple DES was designed to have a 168 bit key, but an attack of complexity 2112 is now known (i.e., Triple DES has 112 bits of security). Nevertheless, as long as the relation between key length and security is sufficient for a particular application, then it doesn't matter if key length and security coincide. This is important for asymmetric-key algorithm, because no such algorithm is known to satisfy this property; elliptic curve cryptography comes the closest with an effective security of roughly half its key length.
I Hope it will help!
^_^
Key length defines the upper-bound on an algorithm's security (i.e., a logarithmic measure of the fastest known attack against an algorithm, relative to the key length), since the security of all algorithms can be violated by brute force attacks. Ideally, key length would coincide with the lower-bound on an algorithm's security. Indeed, most symmetric-key algorithms are designed to have security equal to their key length. However, after design, a new attack might be discovered. For instance, Triple DES was designed to have a 168 bit key, but an attack of complexity 2112 is now known (i.e., Triple DES has 112 bits of security). Nevertheless, as long as the relation between key length and security is sufficient for a particular application, then it doesn't matter if key length and security coincide. This is important for asymmetric-key algorithm, because no such algorithm is known to satisfy this property; elliptic curve cryptography comes the closest with an effective security of roughly half its key length.
I Hope it will help!
^_^
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