In both node.js and OpenSSL, I am seeing cipher "aes-256-gcm".
However, in NIST Special Publication 800-38D, that defines GCM, I am reading:
The underlying block cipher shall be approved, the block size shall be 128 bits, and the key size shall be at least 128 bits.
How is this possible?
I see a similar question has been asked already - GCM encryption for 256-bit and 512-bit block ciphers - but that one is more theoretical question, while in openssl, there is a practical implementation.
Those answers imply that it might be insecure. Is it true, and are the openssl implementations inherently insecure?