replace sha1 with sha256

[IrisesD]

Checklist

• I've tested my changes.
• I've read the Contribution Guidelines.
• I've updated the documentation if necessary.

Motivation and Context

In crypt/crypt.go, the Encrypt and Decrypt functions use SHA-1 as the hash algorithms, which is insecure now because of the collisions. See Finding Collisions in the Full SHA-1
In order to avoid potential attacks, I suggest we replace all SHA-1 uses with SHA-256, which is a recommended algorithm for key management.

Description

1. replace all SHA-1 algorithm uses with SHA-256 algorithm.
2. remove the "crypto/sha1" import