Is your PRIVATE message protected by cryptography?

Dr Ahmed Desoky gave a lecture about Cryptography. The contents incude the history ,concepts, algorithm, the mathematic basis of cryptography.
But the question for me is how realistic the crptography is to us, where this cryptography is used in the real world? I still do not have a clear time table for the development of the cryptography.
Before,the generaly idea about cryptography is that it is used in the commerical, government or other sensitive communication. The price for leaking the message will be a huge cost for the parties who are trying to communicate with each other secretly. So they need to use cryptography to protect this information. After this lecture, I checked the website, find
http://www.garykessler.net/library/crypto.html,
this webpage gave me more information about cryptography, the first documented use of cryptography in writing dates back to circa 1900 B.C

In those days, crptography is far away from the routine life of the ordinary people, it is generally used between the countries or between the leaders of two tribes, they need to exchange the information to unite to fight for the intrusion or something urgent.The algorithm used those days is so simple from today's view, for example caesar cypher

The action of a Caesar cipher is to replace each plaintext letter with one a fixed number of places down the alphabet. This example is with a shift of three, so that a B in the plaintext becomes E in the ciphertext. Interested reader can try this algorithm byhttp://www.secretcodebreaker.com/caesar.html .
It was active for a long period of time during those ancient days.
Today, with the application of computers, this kind of crypher algorithm can be cracked in less than a fraction of second.And with the development of technology and living standards, ordinary people are actually closely related with the cryptography, for example, you usually buy the products with your credit card, you just slide the card in the supermarket terminal, the transcation is completed in a few seconds. In this short period of time, the communication between the terminal which accepted your card and the bank's data processing center is cyphered. So generally this information is unintellgibel to another third party. But remember when some smart guy or powerful enough guy who want to know this information, he may crack this communication, if the benefits to get this information are much larger than the cost. For ordinary people, the information is not important that much, and the cost to crack the crptography utilized by the banks is so high for some evil person. So generally, ordinary people are safe in the eletronic transaction.
Now let us check what kind of cryptography are we using daily, VISA encouraged Any merchant who accepts credit cards must meet PCI DSS, a set of a dozen rules to protect consumer data from hackers.

http://searchsecurity.techtarget.com/originalContent/0,289142,sid14_gci1251180,00.html

The good news for us is that if we can keep our private information such as credit card number private enough, even if the crptography is cracked by some hackers, it is responsiblity of the VISA or other unit. And We should be cautious to protect ourselves.