Look I now what cryptography is I only want to know more about it, more advance knowledge about it. I do have general idea of cryptography. I have tried many websites but I can't seem to understand anything. And it is not because of me, actually I can't find anything that explains or demonstrates properly. Whatever site I go to the words are just thrown in without explanation. Maybe sometimes the word like crypt analysis or symmetric key or public key or cryptosystem are defined but not exactly explained. Even the examples are pointless, for instance to explain encryption and decryption this was the example: "Hello World" is converted to "dsfbUrGiMYTprAfRj4CoBw&ved" is called encryption and turning it back to "Hello World" is decryption. Now tell me how exactly did that simple string got converted into that? I searched that and answer was through a key(something about cipher too.) but well what kind of key and how did that key work? Was it as simple as 1+1=2? There was no explanation to that. All I want to know is how are our password on facebook protected? Whats the difference between passwords used on paypal account and ones used on an ATM? How is the largest prime number related to this topic? What was the first system used on the internet? All I am asking for is good explanation(with as many possible demonstrations as possible.) on this topic so please suggest a website or you can explain it here. I don't mind hard language with tougher words but at least explain those words, and I mean explain not just define it.
Can anyone explain me what cryptography is?
- Thread starter drew96
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UltimateBawb
Honorable
- Aug 13, 2013
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This doesn't seem like a very relevant question for this forum, but I did take a basic cryptography course at university so I'll try and help a bit. I'll be explaining simple ciphers and not the more complex hashes that secure systems use today
Pretty much all ciphers are based around a given key. Say our plain-text is "hello world," our key is "fdsagds," and we are using a basic substitution cipher. First all letters of plain-text and key are converted to their numerical rankings of the alphabet, ranging from 0-25 (A-Z). So we would have plain-text as "7.4.11.11.14 22.14.17.11.3" and key as "6.4.19.1.7.4.19." Then we add the key numbers to the plain-text numbers in order, and if we run out of key numbers we repeat. So our cipher-text will be "(7+6).(4+4).(11+19).(11+1).(14+7).(22+4).(14+19).(17+6).(11+4).(3+19)." However, because our alphabet only has 26 letters we have to convert all addition to mod 26 (look up discrete math if you don't know what this means). So our final text would be "13.8.4.12.21.0.7.23.15.22," which is "N.I.E.M.V.A.H.X.P.W." To decrypt back to plaintext we would simply do the exact same thing except we would -subtract- the key numbers instead of adding.
For a more complex linear cipher you would have a linear equation as a key, say Y=3X+2. To encrypt we would only have to run the equation Y=3X+2 mod 26 for each number-letter of plain-text. To decrypt we would run the cipher-text through the modular inverse of the original equation.
There are many other ciphers but these are some of the more simple ones.
Pretty much all ciphers are based around a given key. Say our plain-text is "hello world," our key is "fdsagds," and we are using a basic substitution cipher. First all letters of plain-text and key are converted to their numerical rankings of the alphabet, ranging from 0-25 (A-Z). So we would have plain-text as "7.4.11.11.14 22.14.17.11.3" and key as "6.4.19.1.7.4.19." Then we add the key numbers to the plain-text numbers in order, and if we run out of key numbers we repeat. So our cipher-text will be "(7+6).(4+4).(11+19).(11+1).(14+7).(22+4).(14+19).(17+6).(11+4).(3+19)." However, because our alphabet only has 26 letters we have to convert all addition to mod 26 (look up discrete math if you don't know what this means). So our final text would be "13.8.4.12.21.0.7.23.15.22," which is "N.I.E.M.V.A.H.X.P.W." To decrypt back to plaintext we would simply do the exact same thing except we would -subtract- the key numbers instead of adding.
For a more complex linear cipher you would have a linear equation as a key, say Y=3X+2. To encrypt we would only have to run the equation Y=3X+2 mod 26 for each number-letter of plain-text. To decrypt we would run the cipher-text through the modular inverse of the original equation.
There are many other ciphers but these are some of the more simple ones.
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