**Cryptography Tutorials - Herong's Tutorial Examples** - v5.42, by Herong Yang

What Is Encryption?

This section describes what is encryption - A bijection function that uses a key, encryption key, to compute the image.

**Encryption Function** - A bijection function that uses a key, encryption key,
to compute the image.

**Clear Text Space** - The domain of an encryption function.

**Cipher Text Space** - The codomain of an encryption function.

**Decryption Function** - The inversion function of an encryption function.
Decryption function also uses a key, decryption key, to compute the image.

**Encryption Scheme** - An algorithm that defines a cleartext space, a ciphertext space,
and a set of encryption keys. For each encryption key, the scheme also defines
an encryption function, a decryption key, and a decryption function. An encryption
scheme is also called a cipher.

**Symmetric Key Encryption** - An encryption scheme that "the decryption
function uses the same key as its encryption function". Symmetric key encryption is
also called one key, or secret key encryption.

**Asymmetric Key Encryption** - An encryption scheme that
"the decryption function uses needs a different key than the key used in its encryption function,
and it is almost impossible to compute one from another". Asymmetric key encryption is
also called public key encryption.

**Block Cipher** - An encryption scheme that "cleartext is broken up into blocks
of fixed length, and encrypted one block at a time".

**Stream Cipher** - An encryption scheme that "cleartext is encrypted as
a continuous stream alphabets".

**Simple Substitution Cipher** - An encryption scheme that "Each alphabet
in the cleartext is substituted by a single alphabet defined by the key".

**Homophonic Substitution Cipher** - An encryption scheme that "Each alphabet
in the cleartext is substituted by an alphabetic string randomly selected
from a set of strings defined by the key".

**Transposition Cipher** - A block cipher that "Alphabets in a block is
permuted in an order defined by the key".

**Product Cipher** - An encryption scheme that "uses multiple ciphers
in which the ciphertext of one cipher is used as the cleartext of
the next cipher". Usually, substitution ciphers and transposition ciphers are used
alternatively to construct a product cipher.

Table of Contents

Introduction to AES (Advanced Encryption Standard)

DES Algorithm - Illustrated with Java Programs

DES Algorithm Java Implementation

DES Algorithm - Java Implementation in JDK JCE

DES Encryption Operation Modes

PHP Implementation of DES - mcrypt

Blowfish - 8-Byte Block Cipher

Secret Key Generation and Management

Cipher - Secret Key Encryption and Decryption

RSA Implementation using java.math.BigInteger Class

Introduction of DSA (Digital Signature Algorithm)

Java Default Implementation of DSA

Private key and Public Key Pair Generation

PKCS#8/X.509 Private/Public Encoding Standards

Cipher - Public Key Encryption and Decryption

OpenSSL Introduction and Installation

OpenSSL Generating and Managing RSA Keys

OpenSSL Generating and Signing CSR

OpenSSL Validating Certificate Path

"keytool" and "keystore" from JDK

"OpenSSL" Signing CSR Generated by "keytool"

Migrating Keys from "keystore" to "OpenSSL" Key Files

Certificate X.509 Standard and DER/PEM Formats

Migrating Keys from "OpenSSL" Key Files to "keystore"