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How does key size affect the strength of a cipher?
Encryption strength is often described in terms of the size of the keys used to perform the encryption: in general, longer keys provide stronger encryption. Key length is measured in bits. Roughly speaking, 128-bit RC4 encryption is 3 x 1026 times stronger than 40-bit RC4 encryption.
Does the larger the size of the key space ensure a more secure cipher?
Is it true the longer the key length is the more secure the encryption? No. Key length does put an upper bound on security, because it determines the complexity of brute force iteration of the key space or factoring, discrete log, etc. for some asymmetric algorithms.
Why are some cryptographic keys much smaller than others?
The length of time a key is good for is also important. Over time computers get faster and techniques for breaking encryption schemes (particuarly techniques for breaking asymmetric encryption) get better. That 512-bit key used for TI calculators probably looked pretty safe when it was first chosen.
Is it possible to attack a 256bit cipher key?
In a sense we do have the really big cipher keys you are talking of. The whole point of a symmetric key is to make it unfeasible to brute-force. In the future, if attacking a 256bit key becomes possible then keysizes will surely increase, but that is quite a ways down the road.
How many keys are there in a symmetric cipher?
That said the basic idea is that the only way to break into a connection secured with a symmetric cipher is to try out all the keys. Which brings us to 128-bit and 256-bit keys. A 128-bit key means there are 340,282,366,920,938,463,463,374,607,431,768,211,456 possible keys to try. number.
Why is asymmetric cryptography good for huge data?
This is because it is simple to use hybrid encryption; we pick a random Symmetric key, encrypt that key with the public key, and then use the Symmetric key to encrypt the data. With this approach, we can handle an arbitrary sized data using any public key encryption method.