Which command is used to create an RSA private key?

Which command is used to create an RSA private key?

• A. ssh-keygen -t rsa -b 2048 -f user.key
• B. openssl genrsa -out user.key 2048
• C. openssl genrsa -out user.key 4096
• D. gpg --gen-key

Answer: (C)

Generating an RSA private key is commonly done with OpenSSL’s key-generation tool. The command openssl genrsa -out user.key 4096 creates a private RSA key and saves it to the file named user.key, using a 4096-bit length. A longer key sharpens security, so 4096 bits is preferred over 2048. The other options either generate keys for different purposes or use shorter or non-RSA key setups: ssh-keygen can create an RSA key for SSH use (not a general-purpose RSA private key file), openssl genrsa -out user.key 2048 produces a valid RSA private key but with weaker 2048-bit strength, and gpg --gen-key makes OpenPGP keys, which may include RSA but are not the direct, standalone RSA private key file described here.

Generating an RSA private key is commonly done with OpenSSL’s key-generation tool. The command openssl genrsa -out user.key 4096 creates a private RSA key and saves it to the file named user.key, using a 4096-bit length. A longer key sharpens security, so 4096 bits is preferred over 2048. The other options either generate keys for different purposes or use shorter or non-RSA key setups: ssh-keygen can create an RSA key for SSH use (not a general-purpose RSA private key file), openssl genrsa -out user.key 2048 produces a valid RSA private key but with weaker 2048-bit strength, and gpg --gen-key makes OpenPGP keys, which may include RSA but are not the direct, standalone RSA private key file described here.