Generating a GPG key to your GitHub

SpiffyEight77 — Sun, 11 Jun 2023 10:53:17 +0000

What is GPG

GPG (GNU Privacy Guard) is an open-source software used for encrypting and signing data. GPG uses asymmetric encryption technology where the cryptographic keys are divided into two parts: a public key and a private key. The public key is used to encrypt data and only the user holding the private key can decrypt it. The private key is used for digital signature which proves that the data indeed comes from a specified sender and has not been tampered with.

Why recommend to use GPG to protect your git commit

There is a risk of Git commit being impersonated because it does not have default authentication mechanisms. If someone knows your name and email address, they can impersonate your commits in the Git repository, which can damage your reputation or lead to improper behavior in your name.

To avoid this, you can use GPG signatures to authenticate Git commits.

Setup GPG in mac

Install GPG

brew install gnupg

Generate key pair

All step set to default

gpg --full-generate-key --expert

Please select what kind of key you want:
   (1) RSA and RSA
   (2) DSA and Elgamal
   (3) DSA (sign only)
   (4) RSA (sign only)
   (7) DSA (set your own capabilities)
   (8) RSA (set your own capabilities)
   (9) ECC (sign and encrypt) *default*
  (10) ECC (sign only)
  (11) ECC (set your own capabilities)
  (13) Existing key
  (14) Existing key from card
Your selection?

Export key

Check the exiting key

gpg --list-secret-keys --keyid-format LONG

gpg: checking the trustdb
gpg: marginals needed: 3  completes needed: 1  trust model: pgp
gpg: depth: 0  valid:   1  signed:   0  trust: 0-, 0q, 0n, 0m, 0f, 1u
[keyboxd]
---------
sec   ed25519/XXXXXXXXXXXX 2023-05-28 [SC]
      XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
uid                 [ultimate] SpiffyEight77
ssb   cv25519/XXXXXXXXXXXX 2023-05-28 [E]

Export the public key

gpg --armor --export XXXXXXXXXXXX

And then past it into GitHub SSH and GPG keys setting.

Setting the environment to the shell

echo 'export GPG_TTY=$(tty)' >> ~/.zshrc && source ~/.zshrc

Allow git to use the GPG key for signing

git config --global user.signingkey XXXXXXXXXXXXX

git config --global commit.gpgsign true

Export for backup (optional)

To export the public and secret key for backup and please keep it in a safe place

gpg --armor --output gpg_sec_key.gpg --export XXXXXXXXXXX
gpg --armor --output gpg_sec_key.gpg --export-secret-keys XXXXXXXXXXX

HackerRank SQL Basic Select

SpiffyEight77 — Sun, 12 Mar 2023 05:40:00 +0000

Before Starting

I haven't handwritten SQL for a long time, but I have recently started practicing again to regain my skills. This post mainly records interesting problems and solutions in SQL Basic Select.

SQL Basic Select

1. Weather Observation Station 4

Find the difference between the total number of CITY entries in the table and the number of distinct CITY entries in the table.

The STATION table is described as follows:

| Field    | Type          | 
|----------|---------------| 
| ID       | NNUMBER       | 
| CITY     | VARCHAR2(21)  | 
| STATE    | VARCHAR2(2)   | 
| LAT_N    | NUMBER        | 
| LONG_W   | NUMBER        |

The objective of this problem is to determine how to utilize the functions COUNT and DISTINCT in order to compute the quantity of answers.

SELECT COUNT(CITY) - COUNT(DISTINCT(CITY))
FROM STATION;

2. Weather Observation Station 5

Query the two cities in STATION with the shortest and longest CITY names, as well as their respective lengths (i.e.: number of characters in the name). If there is more than one smallest or largest city, choose the one that comes first when ordered alphabetically.

The STATION table is described as follows:

| Field    | Type          | 
|----------|---------------| 
| ID       | NNUMBER       | 
| CITY     | VARCHAR2(21)  | 
| STATE    | VARCHAR2(2)   | 
| LAT_N    | NUMBER        | 
| LONG_W   | NUMBER        |

The goal of this problem is to use the UNION 、LIMIT keywords and LENGTH function effectively for querying answers.

(SELECT CITY, LENGTH(CITY)
FROM STATION
ORDER BY LENGTH(CITY) ASC, CITY ASC
LIMIT 1)
UNION
(SELECT CITY, LENGTH(CITY)
FROM STATION
ORDER BY LENGTH(CITY) DESC, CITY ASC
LIMIT 1);

3. Weather Observation Station 8

Query the list of CITY names from STATION which have vowels (i.e., a, e, i, o, and u) as both their first and last characters. Your result cannot contain duplicates.

Input Format

The STATION table is described as follows:

| Field    | Type          | 
|----------|---------------| 
| ID       | NNUMBER       | 
| CITY     | VARCHAR2(21)  | 
| STATE    | VARCHAR2(2)   | 
| LAT_N    | NUMBER        | 
| LONG_W   | NUMBER        |

The goal of this problem is to use the LIKE 、LIMIT keyword effectively for querying answers.

SELECT DISTINCT(CITY)
FROM STATION
WHERE (CITY LIKE 'a%' 
    OR CITY LIKE 'e%' 
    OR CITY LIKE 'i%'
    OR CITY LIKE 'o%'
    OR CITY LIKE 'u%')
AND (CITY LIKE '%a' 
    OR CITY LIKE '%e' 
    OR CITY LIKE '%i'
    OR CITY LIKE '%o'
    OR CITY LIKE '%u');

4. Weather Observation Station 11

Query the list of CITY names from STATION that either do not start with vowels or do not end with vowels. Your result cannot contain duplicates.

Input Format

The STATION table is described as follows:

| Field    | Type          | 
|----------|---------------| 
| ID       | NNUMBER       | 
| CITY     | VARCHAR2(21)  | 
| STATE    | VARCHAR2(2)   | 
| LAT_N    | NUMBER        | 
| LONG_W   | NUMBER        |

The goal of this problem is to use the LIKE 、NOT and OR keyword effectively for querying answers.

SELECT DISTINCT(CITY)
FROM STATION
WHERE NOT (CITY LIKE 'a%' 
    OR CITY LIKE 'e%' 
    OR CITY LIKE 'i%'
    OR CITY LIKE 'o%'
    OR CITY LIKE 'u%')
OR NOT (CITY LIKE '%a' 
    OR CITY LIKE '%e' 
    OR CITY LIKE '%i'
    OR CITY LIKE '%o'
    OR CITY LIKE '%u');

5. Higher Than 75 Marks

Query the Name of any student in STUDENTS who scored higher than 75 Marks. Order your output by the last three characters of each name. If two or more students both have names ending in the same last three characters (i.e.: Bobby, Robby, etc.), secondary sort them by ascending ID.

Input Format

The STUDENTS table is described as follows:

| Colume    | Type         | 
|----------|---------------| 
| ID       | Integer       | 
| Name     | String        | 
| Marks    | Integer       |

The goal of this problem is to use the SUBSTR function for querying answers.

SELECT Name
FROM STUDENTS
WHERE Marks > 75
ORDER BY SUBSTR(Name, -3, 3) ASC, ID ASC;

Forem: SpiffyEight77

Generating a GPG key to your GitHub

What is GPG

Why recommend to use GPG to protect your git commit

Setup GPG in mac

Install GPG

Generate key pair

Export key

Check the exiting key

Export the public key

Setting the environment to the shell

Allow git to use the GPG key for signing

Export for backup (optional)

HackerRank SQL Basic Select

Before Starting

SQL Basic Select

1. Weather Observation Station 4

2. Weather Observation Station 5

3. Weather Observation Station 8

4. Weather Observation Station 11

5. Higher Than 75 Marks