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+#+date: 2020-02-09
+#+title: Cryptography Basics
+
+* Similar Article Available
+
+If you haven't already, feel free to read my post on [[./2018-12-08-aes-encryption.html][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.