Tools which help to measure the complexity ,other type of time complexity.

As a matter of fact I do agree with Atta ur Rehman Khan. You can explain the process as "Reverse Engineering" where you really need to track back each and every process in that particular algorithm. Since no tool was really there to make that algo viz-a-viz no tool could really help you to break it. Furthermore, as Kirchhoff law state that the secrecy of algo lies in the key not the algo. I hope this answers.

I do agree with the above answers and one more parameter is performing randomness tests, the more randomor unpredictable the encrypted data be the more complex will it be and difficult to break.

Not sure if your problem has been solved. Just sharing my thoughts.

In cryptography, asymmetric key cryptosystems can mathematically proven, namely, provable security. The security levels/notions depend on the primitive you are dealing with: encryption, signature, key exchange, identification etc. For encryption, the highest security notion is (adaptive) IND-CCA.

i am not sure for symmetric key cryptosystems as that is not my area, but if I recall correctly, they don't have provably security for that; they become more and more secure or trusted when time goes by :)

There are two rules to Shannon unicity distance and cover time, the last one can calculate the complexity level of security system.

Regards 

The complexity of the cryptosystem depends on the number of operation required in cryptanalysis (not encryption/decrytption) and complexity of each operation.  

Algorithm used in the cryptosystem should be simple and the security should lie on the key. It is kerckhoff principle.

Hence the length of the key decides the number of operations and using complex function (like elliptical curve cryptography over RSA) decides on the time take in each operation.  

The ciphertext should not reveal the statistics of the original plain text.   The statistics of ciphertext and the value of encryption key should be complex.  This property is called diffusion.  It will thwart the attempt to deduce the key.  This property is called diffusion.

The advancement in mathematical and statistical methods used for complex algorithms and parallel computing have reduced the complexity of many cryptosystems substantially.

Good wishes