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With DES using CBC mode, at what point are the blocks of plaintext run through the encryption algorithm? From what i gather all DES-CBC does is XOR the first 64-bit block of plaintext with a random 64-bit number (IV), and then use the resulting cyphertext to XOR with the next block of plaintext, and then simply repeats that ciphertext block XOR'ed with plaintext block process to the end. It sounds like DES isn't even involved in that encryption process.

One more thing, are symmetric block ciphers the only form of encryption that can use modes like CBC, CFB, ECB, and OFB?

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Ipsec Espah wrote: |

With DES using CBC mode, at what point are the blocks of plaintext run through the encryption algorithm? From what i gather all DES-CBC does is XOR the first 64-bit block of plaintext with a random 64-bit number (IV), and then use the resulting cyphertext to XOR with the next block of plaintext, and then simply repeats that ciphertext block XOR'ed with plaintext block process to the end. It sounds like DES isn't even involved in that encryption process.
One more thing, are symmetric block ciphers the only form of encryption that can use modes like CBC, CFB, ECB, and OFB? |

Ok here is the step by step.

1. XOR the plaintext (un-encrypted data) with IV (random data)

2. Encrypt the result

3. XOR the ciphertext (Result from step 2) with next plaintext (un-encrypted data)

4. Encrypt the result.

5. Repeat and rinse until there is no more plaintext.

Usually symmetric ciphers are used for encryption, and public key systems for key exchange. This is done because public key algorithms are much too slow for encryption. There fore even if possible public key algorithms are not usually associated with encryption modes.

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Woops, guess i missed a pretty important step... thanks

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