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Symmetric cryptography includes methods of encryption that are best suited for processing large streams of data. It is distinguished the use of a single key for encrypting and decrypting messages by the sender and receiver.
This type of cryptography is categorized by the use of stream or block ciphers. Stream ciphers operate by encrypting single bits or bytes of information (or plaintext) at a time and implements a feedback mechanism to constantly change the key. Alternatively, block ciphers encrypts data into individual fixed group of bits (a common size is 128 bits) using the same key.
An advantage of symmetric cryptography is that its methods are inexpensive for creating and processing encrypted data. The disadvantage of this example of cryptography is that is both the sender and receiver of the message have to agree on the key. If the key is discovered, the encrypted information becomes compromised.
The following are popular examples of cryptography that have used symmetric encryption:
- International Data Encryption Method (IDEA)
- Advanced Encryption Standard (AES)
- Data Encryption Standard (DES)
- Two Fish is a 128 bit block cipher that uses 128/192/256 bit keys.
- Camelia is similar to AES and uses 128 bit block cipher. Used in 32 bit processors and 8 bit processors (smart cards).
- Misty 1 – Made by Mitsubishi. It is a 128 bit block cipher and used in computer hardware/software.
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Asymmetric cryptography (also called public key cryptography) encryption methods are best used for key exchange and user authentication. This type of cryptography is commonly used in digital signatures. It is distinguished by the use of a private and public key that are created with one-way functions using multiplication and exponentiation. One key is public and published in a public directory while the private key is only known by the receiver of the message.
The following are applications that use asymmetric cryptography:
- Transport Layer Standard (TLS), a communications protocol which is replacing Secure Socket Layer (SSL) for transmitting data over the Internet.
- RSA is used in electronic commerce protocols, software production, key exchange and digital signatures. It implements a variable size encryption block and key.
- PGP (or Pretty Good Privacy) is used for the authentication of data communication and encrypting/decrypting email messages.
- GnuPG/GPG – GNU Privacy Guard is a standard that tracks specifications of OpenPGP.
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Elliptic Curve Cryptography
Elliptic curve cryptography is a standard method used by NIST, NSI and IEEE for government and financial institution use. It is based on public key encryption and used in mobile and wireless environments.
Public keys are created by utilizing the following algebraic equation -
y^2=x^3 + 3 + Ax + B where the x and y points on a curve are used to calculate a public key. The private key is a random number.
The appeal of elliptic curve cryptography is that it offers security with smaller key sizes which result in faster computations, lower power consumption, memory and bandwidth use.
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Quantum cryptography methods use photons to create encrypted keys that can be sent over optical fiber networks by using beams of light. It uses “qubits", which is essentially a computer bit in quantum form. Keys are created using a procedure called quantum key distribution (QKD). In this method, photons are transmitted in horizontal and vertical directions with the use of a laser source over a quantum channel.
A unique property of this example of cryptography is its ability to detect the presence of anyone that tries to obtain the quantum key. Any attempt would be noticed by the sender and receiver by a high increase in the transmission error rate. Since photons cannot be copied or divided keys are virtually unbreakable.
Currently, these types of method can only produce and distribute and encrypted keys. However as of 2010, Japan is working on testing new quantum cryptography methods that can be used to secure video conferencing for government communications.
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Final Thoughts on Cryptography
While there are many examples of cryptography, security of information is never one hundred percent perfect. Even though more complex encryption methods are always being created, sophisticated hackers can learn to adapt and find a way to crack these systems. We just need to try and be one step ahead of the game.
- The image used for this cryptography article was by http://www.sxc.hu/profile/flaivoloka Flavio Takamoto