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+#+title: Cryptography Basics
+#+date: 2020-02-09
+#+description: Learn about the basics of cryptography.
+#+filetags: :security:
+
+* Similar Article Available
+If you haven't already, feel free to read my post on
+[[../aes-encryption/][AES Encryption]].
+
+* What is Cryptography?
+In layman's terms, cryptography is a process that can change data from a
+readable format into an unreadable format (and vice-versa) through a
+series of processes and secrets. More technically, this is the Internet
+Security Glossary's definition:
+
+#+begin_quote
+[Cryptography is] the mathematical science that deals with transforming
+data to render its meaning unintelligible (i.e., to hide its semantic
+content), prevent its undetected alteration, or prevent its unauthorized
+use. If the transformation is reversible, cryptography also deals with
+restoring encrypted data to an intelligible form.
+
+- [[https://tools.ietf.org/html/rfc2828][Internet Security Glossary
+  (2000)]]
+
+#+end_quote
+
+Cryptography cannot offer protection against the loss of data; it simply
+offers encryption methods to protect data at-rest and data in-traffic.
+At a high-level, encrypted is when plaintext data is encrypted to
+ciphertext (a secure form of text that cannot be understood unless
+decrypted back to plaintext). The encryption process is completed
+through the use of a mathematical function that utilizes one or more
+values called keys to encrypt or decrypt the data.
+
+* Key Elements of Cryptographic Systems
+To create or evaluate a cryptographic system, you need to know the
+essential pieces to the system:
+
+- *Encryption Algorithm (Primitive):** A mathematical process that
+  encrypts and decrypts data.
+- *Encryption Key:** A string of bits used within the encryption
+  algorithm as the secret that allows successful encryption or
+  decryption of data.
+- *Key Length (Size):** The maximum number of bits within the encryption
+  key. It's important to remember that key size is regulated in many
+  countries.
+- *Message Digest:** A smaller, fixed-size bit string version of the
+  original message. This is practically infeasible to reverse, which is
+  why it's commonly used to verify integrity.
+
+* Symmetric Systems (Secret Key Cryptography)
+Symmetric cryptography utilizes a secret, bidirectional key to perform
+both encryption and decryption of the data. The most common
+implementation of symmetric cryptography is the Advanced Encryption
+Standard, which uses keys that are 128 bits to 256 bits in size. This
+standard came after the National Institute of Standards and Technology
+(NIST) decided to retire the Data Encryption Standard (DES) in 2001.
+
+Since brute force attacks strongly correlate with key length, the 56-bit
+key length of DES was considered insecure after it was publicly broken
+in under 24 hours. However, there is a modern implementation of DES
+called Triple DES where the DES method is applied three times to each
+data block.
+
+The main advantages to symmetric systems are the ease of use, since only
+one key is required for both encryption and decryption, and the
+simplicity of the algorithms. This helps with bulk data encryption that
+may unnecessarily waste time and power using asymmetric systems.
+
+However, symmetric systems have disadvantages to keep in mind. Since the
+key is private, it can be difficult to safely distribute keys to
+communication partners. Additionally, the key cannot be used to sign
+messages since it's necessary to keep the key private.
+
+* Asymmetric Systems (Public Key Cryptography)
+Asymmetric cryptography utilizes two keys within the system: a secret
+key that is privately-held and a public key that can be distributed
+freely. The interesting aspect of asymmetric cryptography is that either
+key can be used to encrypt the data, there's no rule that dictates which
+key must be used for encryption. Once one key is used to encrypt the
+data, only the other key can be used to decrypt the data. This means
+that if the private key encrypts the data, only the public key can
+decrypt the data.
+
+An advantage of this system is that if you successfully decrypt data
+using one of the keys, you can be sure of the sender since only the
+other key could have encrypted the data.
+
+One of the major implementations of an asymmetric system is a digital
+signature. A digital signature can be generated using the sender's
+private key, or a one-way hash function and is used to provide assurance
+for the integrity and authenticity of the message. A couple common
+message digest algorithms are SHA-256 and SHA-512, which securely
+compress data and produce a 128-bit message digest.
+
+It should be noted that man-in-the-middle attacks are one of the risks
+with digital signatures and public keys. To combat this, applications
+often use a public key infrastructure (PKI) to independently
+authenticate the validity of signatures and keys.
+
+Due to the large key size and
+[[https://crypto.stackexchange.com/a/591][inefficient mathematical
+functions]] of asymmetric encryption, elliptical curve cryptography
+(ECC) is often used to increase security while using fewer resources.
+
+* Applications of Cryptographic Systems
+There are quite a few implementations of cryptographic systems around
+the world. Here are a few popular examples:
+
+*Transport Layer Security (TLS):** One of the most famous cryptographic
+solutions created is TLS, a session-layered or connection-layered
+internet protocol that allows for secure communications between browsers
+and servers. Using handshakes, peer negotiation, and authentication
+allows TLS to prevent eavesdropping and malicious transformation of
+data. The major reason for TLS popularity is that a major vulnerability
+was found in the SSL protocol in 2014. Instead of SSL, TLS can be used
+with HTTP to form HTTPS and is the preferred method for modern web
+development due to its increased security.
+
+*Secure Hypertext Transfer Protocol (HTTPS):** An application layer
+protocol that allows for secure transport of data between servers and
+web clients. One of the unique parts of HTTPS is that it uses a secured
+port number instead of the default web port address.
+
+*Virtual Private Network (VPN):** VPNs are made to securely extend a
+private network across public networks by utilizing an encrypted layered
+tunneling protocol paired with an authentication method, such as
+usernames and passwords. This technology originally allowed remote
+employees to access their company's data but have evolved into one of
+the top choices for anyone who wishes to mask their sensitive personal
+data.
+
+*Internet Protocol Security (IPSec):** This protocol suite facilitates
+communication between two or more hosts or subnets by authenticating and
+encrypting the data packets. IPSec is used in a lot of VPNs to establish
+the VPN connection through the transport and tunnel mode encryption
+methods. IPSec encrypts just the data portion of packets in the
+transport methods, but it encrypts both the data and headers in the
+tunnel method (introducing an additional header for authentication).
+
+*Secure Shell (SSH):** SSH is another network protocol used to protect
+network services by authenticating users through a secure channel. This
+protocol is often used for command-line (shell) functions such as remote
+shell commands, logins, and file transfers.
+
+*Kerberos:** Developed by MIT, Kerberos is a computer-network
+authentication protocol that works on the basis of tickets to allow
+nodes communicating over a non-secure network to prove their identity to
+one another securely. This is most commonly used in business
+environments when used as the authentication and encryption method for
+Windows Active Directory (AD).
+
+* Cybersecurity Controls
+If you're someone who needs solutions on how to control risks associated
+with utilizing a crytograhpic system, start with a few basic controls:
+
+- *Policies:** A policy on the use of cryptographic controls for
+  protection of information is implemented and is in accordance with
+  organizational objectives.
+- *Key management:** A policy on the use, protection and lifetime of
+  cryptographic keys is implemented through the entire application
+  lifecycle.
+- *Key size:** The organization has researched the optimal key size for
+  their purposes, considering national laws, required processing power,
+  and longevity of the solution.
+- *Algorithm selection:** Implemented algorithms are sufficiently
+  appropriate for the business of the organization, robust, and align
+  with recommended guidelines.
+- *Protocol configuration:** Protocols have been reviewed and configured
+  suitable to the purpose of the business.