They use digital signatures, which involves encrypting the hash of the message (in this case, the transaction) with a private key.

I wouldn't call that encryption. It's a distinct primitive.

The process is literally encryption; the distinction comes only from how that encryption is used.

It is definitely not encryption. I believe it initially came from non-interactive zero knowledge protocols. See for example Schnorr signatures: https://cryptologie.net/article/193/schnorrs-signature-and-n...

The process takes a plaintext message (c) and uses a algorithm and a private key to encode it into ciphertext (d), which is then decoded by the recipient using a public key.

What definition of encryption do you use that doesn't fit this process?

It does not encode it into a ciphertext at all. Did you read the article? You do not get back the message, actually there is no way to get back to the message with this signature.

In this case, the hash is the message being encrypted. It's the (c), as I indicated in my previous post. The text being signed is not encrypted, but the signature still involves encryption.

Do you have a source that calls this encryption? Is modular multiplication what you're calling encryption? I'm really confused.

Bytheway definition of encryption: https://en.wikipedia.org/wiki/Encryption

Yeah, but everybody can decrypt it. It's a public key cryptosystem, but it's not going to help fighting against backdoors because it doesn't need one in the first place.