The digital certificate technology mainly used in blockchain is bitcoin. In Bitcoin, digital certificate technology is used to verify the legitimacy and ensure the security of the transaction.

Bitcoin uses public and private keys to generate digital certificates to prove the authenticity and legality of transactions. Each user has a pair of public key and private key. The public key is used to receive bitcoin and the private key is used to initiate transactions. When a user wants to send bitcoin to another user, it is necessary to encrypt the transaction with the public key of the other user, and then sign the transaction with his own private key. The receiver can use its own public key to decrypt the transaction and verify the signature to ensure the authenticity and legality of the transaction.

In addition, Bitcoin also uses elliptic curve digital signature algorithm (ECDSA) to generate digital certificates. The algorithm uses elliptic curve cryptography to generate public and private keys, and uses these keys to verify the authenticity and legality of the transaction.

Compared with other blockchains, Bitcoin is the most widely and deeply used in digital certificate technology. However, other blockchains also use different types of digital certificate technology to ensure the security and authenticity of transactions. For example, Ethereum uses a digital certificate technology called "Meckel Tree" to verify the authenticity and legality of transactions.

In general, digital certificate technology is a very important part of blockchain, which is used to verify the authenticity and legality of transactions and ensure the security and integrity of transactions. Different blockchain uses different types of digital certificate technology, but bitcoin is the most widely and deeply used in this respect.