⭐ Merited by ETFbitcoin (2)
1) Is it correct to say that the cryptographic base used by ASICs is the digital signature?
Nope. A digital signature generally means that a signature is generated that can be authenticated to a known key. ASICs do not do anything like that; they perform SHA256 hashes twice on the block header and they result in a hash.2) Does this mean that encryption is asymmetric?
No. The hashing methods in SHA is Sorry, I was wrong about this piece of info. SHA256 is a hashing algorithm and it is neither symmetrical nor asymmetrical.
3) Is the underlying algorithm SHA256 or ECDSA? I also read double SHA256... I think I've gone a little confused 
Thanks in advance!
C.
SHA256D. Its used to hash block header and the hash is considered in the validity of a block (ie. Determine whether it meets the target).Thanks in advance!
C.
ECDSA is used in the transaction signatures itself. Both is used in the protocol but the mining doesn't consist of ECDSA.