The EDE mode of 3DES relates to the fact that there are two related variants of the feistel network that are used to encrypt the data and decrypt the data. If you "decrypt" the data with a different key, you are effectively encrypting it a second time because the bits will not be anything like what was originally encrypted. As to why this was done, I believe it is to provide backwards compatibility with DES by making k1 and k2 the same, so you do end up with the same data after the first two rounds and then effectively end up with single DES with a key of k3. Seems to me that it would be a really inefficient and niche use case with 3DES hardware having to talk to DES hardware, because presumably if it was a software implementation, the algorithm would just get negotiated down to DES. Maybe if someone has come across a case where this was used IRL, they can educate me...
*i would suggest that EDE3 is similar to a router when it re-encapsulates a packet to forward it to a network, so it hold the information but yeah I agree with the public and global you mentioned **02:04** thanks btw :)*
