Crypto U4, Block Cipher, Electronic Codebook Mode (ECB)

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Encryption

key used with encryption algorithm

to encrypt each block of plaintext

Decryption

key used with decryption algorithm

to decrypt each block of plaintext

Problems

Attacker could reorganize order of

blocks of text without noticing.

Attacker could replay old parts of message.

Attacker could delete blocks of ciphertext

without noticing.

Attacker could repeated blocks without

noticing.

Attacker could mount dictionary

attacks.

Attacker could mount statistical

attacks since the same key is used to encrypt multiple blocks.

How could we improve it?

increase the size of the plaintext

bllocks and cipher alphabets (combat dictionary attacks)

allow some plaintext letters to be

encrypted to different ciphertext letters

make the ciphertext encryption

position dependent

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