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+#+title: AES Encryption
+#+description: Learn how the AES Encryption algorithm works.
+#+date: <2018-11-28 Wed>
+#+filetags: :security:
+
+* 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]]