> “One key, the public key, can only encrypt data, not decrypt it" - this is cryptographically inaccurate. One should use it that way, though.
No, one shouldn’t. To be even more pedantic, verifying a signature under PKI is, in fact, “decrypting with the public key” something (a hash, usually) that was encrypted with the private key. When considering the complete set of PKI operations (encryption + signing), both the public and private parts of a key pair are used in both their enciphering and deciphering capacities.
"No, one shouldn’t" suggests that you don't use public key when encrypting data. "Verifying a signature […] is […] “decrypting with the public key” is the part I meant when writing that the original statement is "cryptographically inaccurate" - it's algorithmically feasible. But also mind that this specific kind of encryption has a specific name - "signing". You can't state that: "no, one shouldn't use public key for encrypting data".
No, one shouldn’t. To be even more pedantic, verifying a signature under PKI is, in fact, “decrypting with the public key” something (a hash, usually) that was encrypted with the private key. When considering the complete set of PKI operations (encryption + signing), both the public and private parts of a key pair are used in both their enciphering and deciphering capacities.