Asymmetric Cryptography

Abstract

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• Also known as Public key Cryptography or Public Private Key
• Achieved with Public Key & Private Key which are mathematically related
• What Public Key encrypts can only be decrypted by Private Key (used in Symmetric Key Exchange)
• What Private Key encrypts can only be decrypted by Public Key (used in Digital Signature)

Convenient

Eliminate the need to exchange keys physically

Computationally Heavy

Compared to Symmetric Cryptography, so we usually use asymmetric cryptography to exchange the symmetric key and use symmetric cryptography for the rest of the secure communication

Verify the keys visually

ssh-keygen -lv -f /path/to/your/key

Obtain RSA pem files

1. Generate a new RSA key pair: openssl genrsa -out <key_name>_private.pem 3096

2. Extract the public key in the right format: openssl rsa -in <key_name>_private.pem -pubout -out <key_name>_public.pem

Public Key

• Distributed to everyone & anyone

Private Key

• Should be kept 100% secret to the owner

Common Asymmetric Cryptography Algo

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RSA

• Rivest-Shamir-Adleman
• An Algorithm used to generate Public Key & Private Key
• Relies on the difficulty of factoring large Composite number into their Prime Number (质数) factor

ECDSA

• Elliptic Curve Digital Signature Algorithm
• An Algorithm used to generate Public Key & Private Key

EdDSA, ED25519

• Edwards-curve Digital Signature Algorithm
• An Algorithm used to generate Public Key & Private Key