Commit `f1f35bd407`

f1f35bd4070c7dd0d232c5a3f2f7373511475565

parent: ceb109db05

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cmc <hello@cleberg.net> · 2025-11-12 01:42 UTC

fix grammar in 2018 posts

Layout: unified · split

content/blog/2018-11-28-aes-encryption.org +45 −44

		@@ -6,15 +6,15 @@
6	6	* Basic AES
7	7
8	8	If you're not familiar with encryption techniques, [[https://en.wikipedia.org/wiki/Advanced_Encryption_Standard][AES]] is the *Advanced
9		Encryption Standard*. This specification was established by the National
10		Institute of Standards and Technology, sub-selected from the Rijndael family of
11		ciphers (128, 192, and 256 bits) in 2001. Furthering its popularity and status,
12		the US government chose AES as their default encryption method for top-secret
13		data, removing the previous standard which had been in place since 1977.
	9	Encryption Standard*. The National Institute of Standards and Technology
	10	established this specification, sub-selected from the Rijndael family of ciphers
	11	(128, 192, and 256 bits) in 2001. Furthering its popularity and status, the US
	12	government chose AES as their default encryption method for top-secret data,
	13	removing the previous standard which had been in place since 1977.
14	14
15		AES has proven to be an extremely safe encryption method, with 7-round and
16		8-round attacks making no material improvements since the release of this
17		encryption standard almost two decades ago.
	15	AES has proven to be a safe encryption method, with 7-round and 8-round attacks
	16	making no material improvements since the release of this encryption standard
	17	almost two decades ago.
18	18
19	19	#+begin_quote
20	20	Though many papers have been published on the cryptanalysis of AES, the fastest
		@@ -26,12 +26,13 @@ slightly more powerful than those proposed 10 years ago [23,24].
26	26
27	27	* How Secure is AES?
28	28
29		In theory, AES-256 is non-crackable due to the massive number of combinations
30		that can be produced. However, AES-128 is no longer recommended as a viable
31		implementation to protect important data.
	29	In theory, AES-256 (AES using a 256-bit key) is non-crackable due to the massive
	30	number of combinations that can the encryption process can produce. However,
	31	AES-128 is no longer recommended as a viable implementation to protect important
	32	data due the 128-bit key's short length.
32	33
33	34	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
34		understand. Basically AES encrypts the data by obscuring the relationship
	35	understand. Basically, AES encrypts the data by obscuring the relationship
35	36	between the data and the encrypted data. Additionally, this method spreads the
36	37	message out. Lastly, the key produced by AES is the secret to decrypting it.
37	38	Someone may know the method of AES, but without the key, they are powerless.
		@@ -40,8 +41,8 @@ To obscure and spread the data out, AES creates a substitution-permutation
40	41	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
41	42	network sends the data through a set of S boxes (using the unique key) to
42	43	substitute the bits with another block of bits. Then, a P box will permutate, or
43		rearrange, the bits. This is done over and over, with the key being derived from
44		the last round. For AES, the key size specifies the number of transformation
	44	rearrange, the bits. This is performed numerous times, with the last round
	45	deriving the key. For AES, the key size specifies the number of transformation
45	46	rounds: 10, 12, and 14 rounds for 128-bit, 192-bit, and 256-bit keys,
46	47	respectively.
47	48
		@@ -49,13 +50,13 @@ respectively.
49	50
50	51	1. KeyExpansion: Using [[https://en.m.wikipedia.org/wiki/Advanced_Encryption_Standard][Rijndael's key schedule]], the keys are dynamically
51	52	generated.
52		2. AddRoundKey: Each byte of the data is combined with this key using bitwise
53		xor.
54		3. SubBytes: This is followed by the substitution of each byte of data.
55		4. ShiftRows: Then, the final three rows are shifted a certain number of
56		steps, dictated by the cipher.
57		5. MixColumns: After the rows have been shifted, the columns are mixed and
58		combined.
	53	2. AddRoundKey: The process combines each byte of the data with the generated
	54	key(s) using bitwise xor.
	55	3. SubBytes: Next, the process substitutes each byte of data.
	56	4. ShiftRows: Then, the process shifts the final three rows a specific number
	57	of steps, dictated by the cipher.
	58	5. MixColumns: Finally, the process mixes and combines the columns into the
	59	final data for this round of processing.
59	60
60	61	This process does not necessarily stop after one full round. Steps 2 through 5
61	62	will repeat for the number of rounds specified by the key. However, the final
		@@ -66,42 +67,42 @@ weakness).
66	67
67	68	According to research done by Bogdanov et al., it would take billions of years
68	69	to brute force a 126-bit key with current hardware. Additionally, this brute
69		force attack would require storing 2^{88} bits of data! However, there are a few
70		different attacks that have been used to show vulnerabilities with the use of
71		this technology. Side-channel attacks use inadvertent leaks of data from the
72		hardware or software, which can allow attackers to obtain the key or run
73		programs on a user's hardware.
	70	force attack would require storing 2^{88} bits of data! However, people have
	71	shown different attacks displaying vulnerabilities with the use of this
	72	technology. Side-channel attacks use inadvertent leaks of data from the hardware
	73	or software, which can allow attackers to obtain the key or run programs on a
	74	user's hardware.
74	75
75	76	Please note that this is not something you should run out and try to implement
76		in your =Hello, World!= app after only a few hours of research. While AES
77		(basically all encryption methods) is extremely efficient in what it does, it
78		takes a lot of time and patience to understand. If you're looking for something
79		which currently implements AES, check out the [[https://www.bouncycastle.org/documentation.html][Legion of the Bouncy Castle]] for
80		Java implementations of cryptographic algorithms.
	77	in your =Hello, World!= application after only hours of research. While AES
	78	(basically all encryption methods) is efficient in what it does, it takes a lot
	79	of time and patience to understand. If you're looking for something which
	80	currently implements AES, check out the [[https://www.bouncycastle.org/documentation.html][Legion of the Bouncy Castle]] for Java
	81	implementations of cryptographic algorithms.
81	82
82	83	* Why Does Encryption Matter?
83	84
84	85	There are limitless reasons to enable encryption at-rest or in-transit for
85		various aspects of your digital life. You can research specific examples, such
86		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
87		list a few basic reasons to always enable encryption, where feasible:
	86	aspects of your digital life. You can research specific examples, such as
	87	[[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
	88	list basic reasons to always enable encryption, where feasible:
88	89
89		1. Privacy is a human right and is recognized as a national right in some
90		countries (e.g., [[https://www.law.cornell.edu/wex/fourth_amendment][US Fourth Amendment]]).
	90	1. Privacy is a human right and some countries recognize it as a national right
	91	(e.g., [[https://www.law.cornell.edu/wex/fourth_amendment][US Fourth Amendment]]).
91	92	2. "Why not?" Encryption rarely affects performance or speed, so there's usually
92	93	not a reason to avoid it in the first place.
93	94	3. Your digital identity and activity (texts, emails, phone calls, online
94		accounts, etc.) are extremely valuable and can result in terrible
95		consequences, such as identity theft, if leaked to other parties. Encrypting
96		this data prevents such leaks from ruining lives.
	95	accounts, etc.) are valuable and can result in consequences, such as identity
	96	theft, if leaked to other parties. Encrypting this data prevents such leaks
	97	from ruining lives.
97	98	4. Wiping or factory-resetting does not actually wipe all data from the storage
98	99	device. There are methods to read data from the physical disks/boards inside
99	100	devices.
100		5. Corporations, governments, and other nefarious groups/individuals are
101		actively looking for ways to collect personal information about anyone they
102		can. If someone's data is unencrypted, that person may become a target due to
103		the ease of data collection.
	101	5. Corporations, governments, and other groups or individuals are actively
	102	looking for ways to collect personal information about anyone they can. If
	103	someone's data is not encrypted, that person may become a target due to the
	104	ease of data collection.
104	105
105		Read More:
	106	* Read More
106	107
107	108	- [[http://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.197.pdf][Federal Information Processing Standards Publication 197]]

content/blog/2018-11-28-cpp-compiler.org +24 −22

		@@ -8,10 +8,10 @@
8	8	[[https://en.wikipedia.org/wiki/C%2B%2B][C++]] is a general-purpose programming language with object-oriented, generic, and
9	9	functional features in addition to facilities for low-level memory manipulation.
10	10
11		The source code, shown in the snippet below, must be compiled before it can be
12		executed. There are many steps and intricacies to the compilation process, and
13		this post was a personal exercise to learn and remember as much information as I
14		can.
	11	A developer must compile source code, such as the example shown in the snippet
	12	below, before they can execute the compiled program. There are numerous steps
	13	and intricacies to the compilation process, and this post was a personal
	14	exercise to learn and remember as much information as I can.
15	15
16	16	#+begin_src cpp
17	17	#include <iostream>
		@@ -36,9 +36,10 @@ is not the only compiled language. Check out [[https://en.wikipedia.org/wiki/Com
36	36	languages]] for more examples of compiled languages.
37	37
38	38	I'll start with a wonderful, graphical way to conceptualize the C++ compiler.
39		View [[https://web.archive.org/web/20190419035048/http://faculty.cs.niu.edu/~mcmahon/CS241/Notes/compile.html][The C++ Compilation Process]] by Kurt MacMahon, an NIU professor, to see the
40		graphic and an explanation. The goal of the compilation process is to take the
41		C++ code and produce a shared library, dynamic library, or an executable file.
	39	View [[https://web.archive.org/web/20190419035048/http://faculty.cs.niu.edu/~mcmahon/CS241/Notes/compile.html][The C++ Compilation Process]] by Kurt MacMahon, a Northern Illinois
	40	University (NIU) professor, to see the graphic and an explanation. The goal of
	41	the compilation process is to take the C++ code and produce a shared library,
	42	dynamic library, or an executable file.
42	43
43	44	** Compilation Phases
44	45
		@@ -61,10 +62,11 @@ the expanded code.
61	62
62	63	*** Step 2
63	64
64		After the code is expanded, the compiler comes into play. The compiler takes the
65		C++ code and converts this code into the assembly language, understood by the
66		platform. You can see this in action if you head over to the [[https://godbolt.org][GodBolt Compiler
67		Explorer]], which shows C++ being converted into assembly dynamically.
	65	After the compiler expands the code, the compiler comes into play. The compiler
	66	takes the C++ code and converts this code into the assembly language, understood
	67	by the platform. You can see this in action if you head over to the [[https://godbolt.org][GodBolt
	68	Compiler Explorer]], which shows the compiled converting C++ into assembly
	69	dynamically.
68	70
69	71	For example, the =Hello, world!= code snippet above compiles into the following
70	72	assembly code:
		@@ -113,17 +115,17 @@ _GLOBAL__sub_I_main:
113	115
114	116	*** Step 3
115	117
116		Third, the assembly code generated by the compiler is assembled into the object
117		code for the platform. Essentially, this is when the compiler takes the assembly
118		code and assembles it into machine code in a binary format. After researching
119		this online, I figured out that a lot of compilers will allow you to stop
120		compilation at this step. This would be useful for compiling each source code
121		file separately. This saves time later if a single file changes; only that file
122		needs to be recompiled.
	118	Third, the compiled assembles the assembly code into the object code for the
	119	platform. Essentially, this is when the compiler takes the assembly code and
	120	assembles it into machine code in a binary format. After researching this
	121	online, I figured out that a lot of compilers will allow you to stop compilation
	122	at this step. This would be useful for compiling each source code file
	123	separately. This saves time later if a single file changes, since the developer
	124	will only need to re-compile single file.
123	125
124	126	*** Step 4
125	127
126		Finally, the object code file generated by the assembler is linked together with
127		the object code files for any library functions used to produce a shared
128		library, dynamic library, or an executable file. It replaces all references to
129		undefined symbols with the correct addresses.
	128	Finally, the compiler links the object code file generated by the assembler
	129	together with the object code files for any library functions used to produce a
	130	shared library, dynamic library, or an executable file. It replaces all
	131	references to undefined symbols with the correct addresses.

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