9618 · 17.1
Encryption, Encryption Protocols and Digital Certificates flashcards
Revision flashcards for Cambridge 9618 Encryption, Encryption Protocols and Digital Certificates (syllabus 17.1). Flip, recall, then mark a real past-paper question.
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Plaintext
The original, unencrypted data or message that is readable by a human or computer.
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Ciphertext
The result of encrypting plaintext. It is unreadable without the correct key and decryption algorithm.
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Symmetric Key Encryption
An encryption method where the same key is used for both encryption and decryption. It's fast but has a key distribution problem.
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Trap: Why isn't symmetric encryption enough on its own for the internet?
The 'key distribution problem'. Securely sharing the single secret key with the recipient beforehand is a major challenge over an insecure network like the internet.
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Asymmetric Key Encryption
An encryption method that uses a pair of keys: a public key for encryption and a private key for decryption. Also known as public-key cryptography.
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Trap: Why not use asymmetric encryption for all communication?
It is computationally intensive and much slower than symmetric encryption. It's typically only used to establish an initial secure channel or for digital signatures.
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Public Key
In asymmetric encryption, this key is made available to everyone. It is used to encrypt data intended for the owner of the corresponding private key.
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Private Key
In asymmetric encryption, this key is kept secret by its owner. It is used to decrypt data that was encrypted with the corresponding public key.
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SSL/TLS (Secure Sockets Layer / Transport Layer Security)
Cryptographic protocols that provide secure communication over a computer network. TLS is the modern, more secure successor to SSL.
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Digital Certificate
An electronic document used to prove the ownership of a public key. It binds a public key to an identity (e.g., a website domain) and is issued by a Certificate Authority.
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Certificate Authority (CA)
A trusted entity that issues, manages, and revokes digital certificates. Browsers have a pre-installed list of trusted CAs.
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Session Key
A temporary, single-use symmetric key used for encrypting all messages in one communication session (e.g., during a TLS connection). It is generated after the initial asymmetric key exchange.