Anyone know of any good cryptography tutorials?

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Anyone know of any good cryptography tutorials?

Post by ghostheadx2 on Fri Jun 19, 2015 10:07 pm
([msg=88584]see Anyone know of any good cryptography tutorials?[/msg])

I'm working on networking tutorials and java right now. But I'm just watching videos on how networks work. I'd like to know if there are any good cryptography tutorials, especially in video form. I'd really appreciate it. I want something that goes from beginner through intermediate or advanced. Thanks.
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Re: Anyone know of any good cryptography tutorials?

Post by Dark Star1000 on Sat Jun 20, 2015 2:56 am
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Hope they are helpful.
If you need more Google if your friend. Just google it and you will get what you need.
http://www.ibm.com/developerworks/tivoli/tutorials/s-crypto/s-crypto.html
http://support.gpgtools.org/kb/how-to/introduction-to-cryptography
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Re: Anyone know of any good cryptography tutorials?

Post by parakkafaith on Sat Jun 20, 2015 6:20 am
([msg=88592]see Re: Anyone know of any good cryptography tutorials?[/msg])

ghostheadx2 wrote:I'm working on networking tutorials and java right now. But I'm just watching videos on how networks work. I'd like to know if there are any good cryptography tutorials, especially in video form. I'd really appreciate it. I want something that goes from beginner through intermediate or advanced. Thanks.


Cryptography isn't like programming languages in the sense that you can snag tutorials to learn it. Sure, you can look up neat bits about how some of the more interesting historical codes and ciphers work, but you're certainly not going to be learning cryptography this way if your goal is to reach anything intermediate or advanced. When you take a computer science course, you're most definitely going to be given programming lessons with any number of different programming languages. When you take a cryptography course, you're going to be given lessons in cryptography using maths that aren't learned by typing "cryptography tutorials" into google. When you google "How to become a dentist", there are reasons every resource tells you to go to school.

Now that that's out of the way, you're going to love this. Trust me.

What you're seeing now is fun beginner stuff, for the hobbyist.

This is a cryptography course. (Fairly self contained, so you don't need to be an experienced mathematician to pick it up)

And this. This is what is known as a cryptography course that has ascended past a cryptography course. Or, you could just call this cryptography 2.

And this is to go even further beyond

Sorry that took so long.
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Re: Anyone know of any good cryptography tutorials?

Post by ghost107 on Sat Jun 20, 2015 7:00 am
([msg=88594]see Re: Anyone know of any good cryptography tutorials?[/msg])

You should read your old posts(1 month old):
viewtopic.php?f=28&t=12253

For cryptography would require to know math, also there are some math concepts that you didn't learned in school yet. So I'm gonna give you a quick introduction.

Symmetric Encryption:
Substitution cipher
Substitution(replacement) is the simplest method for encryption. The Idea is very simple it substitue each letter with another letter from the alphabet.
Example:
Code: Select all
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Z I R A J S B K T C L U D M V E N W F O X G P Y H Q


Attacks:
  1. Brute Force: A brute force attack checks for every substituted alphabet possible, also known as Exhaustive key search.
    https://en.wikipedia.org/wiki/Brute-force_attack
  2. Letter Frequency Analysis:
    https://en.wikipedia.org/wiki/Frequency_analysis

Shift Cipher (or Caesar Cipher)
This cypher is a substitution cipher with a simple mathematical description, shifts the plaintext letter by a number of positions in the same alphabet.
Code: Select all
A B C D E F G H I J K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

P =  Plaint text, C  = Cyphertext, i = index of the element, k =  key
Encryption: Ci = (Pi + k) mod 26
Decryption: Pi = (Ci- k) mod 26


Improvement to Caesar Cipher:
- Affine Sipher
This cypher adds a multiplication of the shift cypher with another part of the key.
Code: Select all
k -  key composed of a, b,
Encryption: Ci = (a* Pi + b) mod 26
Decryption: Pi = ((Ci- b)/a) mod 26


Attacks:
Since it is a very simple substitution algorithm, this cipher has 2 attacks( Brute Force Attack, and Letter Frequency Analysis)

Stream Ciphers
A stream cypher encrypts the bits individually(the key is generated, using a key stream generator), look into bitwise operations. Can be broken using Linear cryptanalysi.
Read about:
  • Pseudorandom Number Generators (PRNG)
  • True Random Number Generators (TRNG)
  • Cryptographically Secure Pseudorandom Number Generators (CSPRNG)
  • One-Time-Pad
Block Ciphers
Definition:
A block cypher encrypts an entire block of plain text bits at a time with the same key.

DES (Data Encryption Standard)
Not gonna write a description on DES already wrote on my previous post, or google for more details.

Attacks:
  • Brute Force:
    - The key space is too small , so it can be attacked by using brute force
  • Analytical Attacks
    - Differential cryptanalysis
    - Linear cryptanalysis
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