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Modern private key ciphers (Examples (FEAL (NTT, Japan, 1990) key -- 128…
Modern
private
key ciphers
Examples
FEAL (NTT, Japan, 1990)
key -- 128 bits, plaintext/ciphertext -- 64 bits
IDEA (Lai & Massey, Swiss, 1991)
key -- 128 bits, plaintext/ciphertext -- 64 bits
LOKI (ADFA, Australia, 1989)
key, plaintext/ciphertext -- 64 bits
SPEED (Y Zheng in 1996)
Key/(plaintext/ciphertext) -- 48,64,80,…,256 bits
DES (US, 1977) (3DES)
key -- 56 bits, plaintext/ciphertext -- 64 bits
AES (Joan Daemen & Vincent Rijmen 2000)
Key/(plaintext/ciphertext) -- 128, 192 and 256 bits
Symmetric Key Distribution options
If A and B have previously and recently used a key, one party could transmit the new key to the other, using the old key to encrypt the new key
If A and B each have an encrypted connection to a third party C, C could deliver a key on the encrypted links to A and B
A key can be selected by A and physically delivered to B
A third party can select the key and physically deliver it to A and B
Symmetric-Key DistributionTechniques
Symmetric-Key without Server
Symmetric-Key with Server
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Session key:
Data encrypted with a one-time session key. At the conclusion of the session the key is destroyed.
Permanent key:
Used between entities for the purpose of distributing session keys.
GENERAL
Single, secret key
Key distribution problem of secret key systems
Establish key before communication
Do NOT provide electronic signatures (no third party authentication)
Faster than public-key encryption