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Based on this, it looks like something slightly wrong. What would need to be adjusted at the transmitter side to allow the receiver to decrypt the message/data?

Joel Goerge
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    A better question might be: "I don't understand this because ..." instead of something is wrong. What part do you not understand? – zaph Aug 14 '18 at 21:06

1 Answers1

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There is nothing wrong. This is 3DES with two keys.

The Decryption operation precisely undoes the Encryption operation.

The right E in Encryption is undone by the left D in Decryption, the middle D in Encryption is undone by the middle E in Decryption, the left E in Encryption is undone by the right D in Decryption.

For a rigorous proof that using D in the encryption still allows decryption, see this. For an explanation of why the D in the encryption, see this. These are for 3DES with 3 keys, but the reasoning applies to 2 keys as well.

fgrieu
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  • The answer might be better if why EDE/DED was chosen and not EEE/DDD. The D in encrypt and E in decrypt might be what the OP is concerned about. – zaph Aug 14 '18 at 23:30
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    @zaph: if so they could look at https://crypto.stackexchange.com/questions/2060/why-do-we-use-encrypt-decrypt-encrypt-ede-in-3des-rather-than- (and several others linked to it) – dave_thompson_085 Aug 15 '18 at 03:10