File encryption and decryption technology in Linux: GnuPG

GnuPG (GNU Privacy Guard or GPG): encryption and signature software based on the PGP (Pretty Good Privacy) mechanism in Linux

PGP (Pretty Good Privacy) is a mail encryption software based on the RSA public key encryption system. It not only keeps users' data confidential, but also prevents unauthorized users from reading it and can add digital signatures to emails, this ensures that the email is sent by you. This allows people to securely communicate with people they have never seen before, without any confidential channels in advance for key delivery.

GnuPG is a collection of tools for secure communication and data storage. It supports data encryption and digital signatures.

In terms of functionality, it is the same as PGP, but PGP uses the IDEA patented algorithm, and PGP will have license issues. GnuPG does not use this algorithm, therefore, there are no restrictions on user use.

GnuPG supports the following algorithms.

Public Key: RSA, RSA-E, RSA-S, ELG-E, and DSA

Symmetric encryption: 3DES, CAST5, BLOWFISH, AES, AES192, AES256, TWOFISH

Hash: MD5, SHA1, RIPEMD160, SHA256, SHA384, and SHA512

Compression: no compression, ZIP, ZLIB, BZIP2

Gpg Command [Option] [file name]
Command:
-S, -- sign [file name] to generate a signature
-- Clearsign [file name] generates a plaintext Signature
-B, -- detach-sign to generate a separate Signature
-E, -- encrypt: encrypt data
-C, -- encryption Ric only uses symmetric encryption
-D, -- decrypt data (default)
-- Verify verification signature
-- List-keys
-- List-sigs: list keys and signatures
-- Check-sigs: List and check the Key signature
-- Fingerprint: List keys and fingerprints
-K, -- list-secret-keys to list private keys
-- Gen-key generates a new pair of key pairs
-- Delete-keys: delete the key from the Public Key Ring
-- Delete-secret-keys: delete the key from the key ring of the private key.
-- Sign-key: Add a signature for a key
-- Lsign-key: Add a local signature for a key
-- Edit-key: edit a key or add a signature for it
-- Gen-revoke generates a revocation Certificate
-- Export
-- Send-keys: exports the key to a public key server.
-- Recv-keys import the key from the Public Key Server
-- Search-keys: search for keys on the Public Key Server
-- Refresh-keys update all local keys from the Public Key Server
-- Import/merge keys
-- Card-status print card status
-- Card-edit: change the data on the card
-- Change-pin: change the card's PIN
-- Update-trustdb update trust Database
-- Print-md algorithm [file] use the specified hash algorithm to print the message hash value
Option:
-A, -- armor output is encapsulated in ASCII
-R, -- recipient is the recipient's "A." Encryption
-U, -- local-user use this user ID to sign or decrypt
-Z N: Set the compression level to N (0 indicates no compression)
-- Textmode uses the standard text mode
-O, -- output specifies the output file
-V, -- verbose detailed mode
-N, -- dry-run is not changed
-I, -- ask before interactive Overwrite
-- Openpgp behaviors strictly follow OpenPGP Definitions
-- Pgp2 generates packets compatible with PGP 2.x

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