Protects confidentiality and integrity of data during transmission or storage.
Plain data is converted to ciphertext in the process of encryption. A key is used in the process. Similarly, decryption converts the ciphertext back to the original data using a (same or different) key. Security depends on the secrecy of the keys, and not the algorithms.
Terminology
Ciphertext means the encrypted message.
- sender: origin of message
- recipient: intended receiver
- plaintext: original message
- ciphertext: encrypted message
- encryption: converting plaintext to ciphertext
- decryption: reverse process
- cryptosystem: overall system of algorithms and keys
Symmetric Encryption
Uses a single key for both encryption and decryption. Key must remain secret between sender and receiver.
Fast to generate. Efficient for large data. Difficult to safely share the key.
Asymmetric Encryption
Uses a pair of keys: public and private. Public key is shared publicly. Private key is not shared. Messages encrypted with one key, can only be decrypted by the other.
Easy key distribution. No shared secrets required. Slower than symmetric.
Digital Signature
Authenticity and integrity of a message. Created using sender’s private key. Verified using sender’s public key.
Digital Certificate
A digital certificate binds a public key to an identity. Issued and signed by a Certificate Authority. They verify the identity before issuing certificates. Enables trust in public key systems.