OpenSSL:
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> File Encryption:
openssl enc -aes-256-cbc -salt -in file.input -out file.enc

> File Decryption:
openssl enc -d -aes-256-cbc -in file.enc -out file.output

> Generate a private key:
openssl genrsa -aes256 -out private.key 4096

> Get Public Key:
openssl rsa -in private.key -pubout -out public.key

> Encrypt a file using PUBLIC KEY:
openssl pkeyutl -encrypt -in test.txt -out test.txt.enc -pubin -inkey public.key

> Decrypt a file using PRIVATE KEY:
openssl pkeyutl -decrypt -in test.txt.enc -out test.txt -inkey private.key