Encryption
| English | Chinese | Pinyin |
|---|---|---|
| encryption | 加密 | jiā mì |
| intercepted | 拦截 | lán jié |
| plaintext | 明文 | míng wén |
| ciphertext | 密文 | mì wén |
| symmetric | 对称 | duì chèn |
| asymmetric | 非对称 | fēi duì chèn |
| key | 密钥 | mì yào |
| public key | 公钥 | gōng yào |
| private key | 私钥 | sī yào |
Scrambling a message
- Encryption 加密 scrambles data so it can't be understood if it is intercepted 拦截.
- Readable data is plaintext 明文; scrambled data is ciphertext 密文.
- There are two kinds: symmetric 对称 and asymmetric 非对称.
What encryption does (and doesn't)
- Encryption uses a key 密钥 to turn plaintext into ciphertext, and back again to decrypt.
- It does not stop data from being intercepted — it only stops the intercepted data from being understood.
Symmetric uses one shared key; asymmetric uses a public key 公钥 to encrypt and a private key 私钥 to decrypt.
What does encryption achieve?
Encryption scrambles data so interception is useless — it does not prevent the interception itself.
Symmetric encryption
- Symmetric encryption uses a single key to both encrypt and decrypt.
- The sender and receiver must share this same secret key.
- The risk: the key itself could be stolen while being shared.
Simplex is one way only; half-duplex is both ways but one at a time; full-duplex is both ways at once.
A shift cipher (symmetric key)
Caesar's cipher shifts every letter forward by a fixed key. The SAME key encrypts and decrypts — that is what symmetric means. Slide the key and try to read it without knowing the shift.
Match each encryption term to its meaning.
Plaintext → (key) → ciphertext; symmetric shares one key, asymmetric uses a public/private pair.
Symmetric encryption uses:
Symmetric uses one secret key that both sides must share — the risk is that key being stolen.
Asymmetric encryption
- Asymmetric encryption uses two keys: a public key (anyone can have it, used to encrypt) and a private key (kept secret, used to decrypt).
- Data encrypted with the public key can only be decrypted with the matching private key.
- The secret key never has to be shared, so it is safer than symmetric.
In asymmetric encryption, data is encrypted with the ____ key and decrypted with the ____ key.
The public key encrypts; only the matching private key can decrypt — so the secret key is never shared.
Asymmetric encryption is safer for sharing because only the public key is ever sent — the private key that decrypts the data never has to be shared.
Symmetric encryption's weak point is getting the shared key to the other side safely; asymmetric removes that by keeping the private key secret.
You've got it
- encryption makes intercepted data unreadable (it doesn't prevent interception)
- plaintext → ciphertext using a key
- symmetric = one shared key (risk: sharing it); asymmetric = public key encrypts, private key decrypts
- asymmetric is safer because the secret key is never shared