如何使用公钥验证数字签名？

Question

I am doing a project about Cryptocurrency. I am given a pair of public key and private key for one user. Here is how I sign my data:

sig = this.hash(trans.details +trans.privKey);

The hash function is provided. My question is how to verify this signature with a given public key?

I have tried this

var v = this.hash(trans.details+"");

: var v2=this.hash(sig+trans.pubKey); I compared these two hash value, they are not the same. For my understanding, there is a way to have these match each other so that I could say the signature is valid.

Note: Public key and Private key are given in this project. So they should be correct.

What am I missing? Any ideas?

Answer 1

You can't. That signature scheme doesn't work.

The linkage between a private key and its corresponding public key only exist within the cryptographic algorithm that generated those keys. (For instance, if you had an RSA key pair, you would need to use the RSA algorithm to generate signatures.) Inserting the private key into a general-purpose hash function has no meaningful effect.

Generally speaking, signatures are generated by taking an unsalted hash of the data to be signed, then encrypting the resulting hash using the private key, eg

let signature = RSA_encrypt(H(message), private_key)

The public key can then be used to decrypt the hash, proving that it was generated using the appropriate private key:

let signature_ok = equal(H(message), RSA_decrypt(signature, public_key))