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+#+title: AES Encryption
+#+date: <2018-11-28>
+#+description: A beginner's guide to AES encryption.
+
+* Basic AES
+
+If you're not familiar with encryption techniques,
+[[https://en.wikipedia.org/wiki/Advanced_Encryption_Standard][AES]] is
+the *Advanced Encryption Standard*. This specification was established
+by the National Institute of Standards and Technology, sub-selected from
+the Rijndael family of ciphers (128, 192, and 256 bits) in 2001.
+Furthering its popularity and status, the US government chose AES as
+their default encryption method for top-secret data, removing the
+previous standard which had been in place since 1977.
+
+AES has proven to be an extremely safe encryption method, with 7-round
+and 8-round attacks making no material improvements since the release of
+this encryption standard almost two decades ago.
+
+#+begin_quote
+Though many papers have been published on the cryptanalysis of AES, the
+fastest single-key attacks on round-reduced AES variants [20, 33] so far
+are only slightly more powerful than those proposed 10 years ago
+[23,24].
+
+- [[http://research.microsoft.com/en-us/projects/cryptanalysis/aesbc.pdf][Bogdonav,
+  et al.]]
+#+end_quote
+
+* How Secure is AES?
+
+In theory, AES-256 is non-crackable due to the massive number of
+combinations that can be produced. However, AES-128 is no longer
+recommended as a viable implementation to protect important data.
+
+A semi-short
+[[http://www.moserware.com/2009/09/stick-figure-guide-to-advanced.html][comic
+strip]] from Moserware quickly explains AES for the public to
+understand. Basically AES encrypts the data by obscuring the
+relationship between the data and the encrypted data. Additionally, this
+method spreads the message out. Lastly, the key produced by AES is the
+secret to decrypting it. Someone may know the method of AES, but without
+the key, they are powerless.
+
+To obscure and spread the data out, AES creates a
+substitution-permutation network. Wikipedia has a wonderful
+[[https://upload.wikimedia.org/wikipedia/commons/thumb/c/cd/SubstitutionPermutationNetwork2.png/468px-SubstitutionPermutationNetwork2.png][example
+of an SP network]] available. This network sends the data through a set
+of S boxes (using the unique key) to substitute the bits with another
+block of bits. Then, a P box will permutate, or rearrange, the bits.
+This is done over and over, with the key being derived from the last
+round. For AES, the key size specifies the number of transformation
+rounds: 10, 12, and 14 rounds for 128-bit, 192-bit, and 256-bit keys,
+respectively.
+
+* The Process
+
+1. *KeyExpansion*: Using
+   [[https://en.m.wikipedia.org/wiki/Advanced_Encryption_Standard][Rijndael's
+   key schedule]], the keys are dynamically generated.
+2. *AddRoundKey*: Each byte of the data is combined with this key using
+   bitwise xor.
+3. *SubBytes*: This is followed by the substitution of each byte of
+   data.
+4. *ShiftRows*: Then, the final three rows are shifted a certain number
+   of steps, dictated by the cipher.
+5. *MixColumns*: After the rows have been shifted, the columns are mixed
+   and combined.
+
+This process does not necessarily stop after one full round. Steps 2
+through 5 will repeat for the number of rounds specified by the key.
+However, the final round excludes the MixColumns step. As you can see,
+this is a fairly complex process. One must have a solid understanding of
+general mathematic principles to fully understand how the sequence works
+(and to even attempt to find a weakness).
+
+According to research done by Bogdanov et al., it would take billions of
+years to brute force a 126-bit key with current hardware. Additionally,
+this brute force attack would require storing 2^{88} bits of data!
+However, there are a few different attacks that have been used to show
+vulnerabilities with the use of this technology. Side-channel attacks
+use inadvertent leaks of data from the hardware or software, which can
+allow attackers to obtain the key or run programs on a user's hardware.
+
+Please note that this is not something you should run out and try to
+implement in your =Hello, World!= app after only a few hours of
+research. While AES (basically all encryption methods) is extremely
+efficient in what it does, it takes a lot of time and patience to
+understand. If you're looking for something which currently implements
+AES, check out the
+[[https://www.bouncycastle.org/documentation.html][Legion of the Bouncy
+Castle]] for Java implementations of cryptographic algorithms.
+
+* Why Does Encryption Matter?
+
+There are limitless reasons to enable encryption at-rest or in-transit
+for various aspects of your digital life. You can research specific
+examples, such as
+[[https://arstechnica.com/tech-policy/2018/12/australia-passes-new-law-to-thwart-strong-encryption/][Australia
+passes new law to thwart strong encryption]]. However, I will simply
+list a few basic reasons to always enable encryption, where feasible:
+
+1. Privacy is a human right and is recognized as a national right in
+   some countries (e.g.,
+   [[https://www.law.cornell.edu/wex/fourth_amendment][US Fourth
+   Amendment]]).
+2. "Why not?" Encryption rarely affects performance or speed, so there's
+   usually not a reason to avoid it in the first place.
+3. Your digital identity and activity (texts, emails, phone calls,
+   online accounts, etc.) are extremely valuable and can result in
+   terrible consequences, such as identity theft, if leaked to other
+   parties. Encrypting this data prevents such leaks from ruining lives.
+4. Wiping or factory-resetting does not actually wipe all data from the
+   storage device. There are methods to read data from the physical
+   disks/boards inside devices.
+5. Corporations, governments, and other nefarious groups/individuals are
+   actively looking for ways to collect personal information about
+   anyone they can. If someone's data is unencrypted, that person may
+   become a target due to the ease of data collection.
+
+*Read More:*
+
+- [[http://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.197.pdf][Federal
+  Information Processing Standards Publication 197]]