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diff --git a/content/blog/2018-11-28-aes-encryption.org b/content/blog/2018-11-28-aes-encryption.org index 64b8f29..8e7dff6 100644 --- a/content/blog/2018-11-28-aes-encryption.org +++ b/content/blog/2018-11-28-aes-encryption.org @@ -5,121 +5,103 @@ * 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. +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]. +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.]] +- [[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 +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. +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 +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. +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. + 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]] +- [[http://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.197.pdf][Federal Information Processing Standards Publication 197]] |