如何将密码：：sha2：：sha2 256散列转换为&[u8]表示？

Question

我目前正在尝试从一个ED25519哈希(通过rust-crypto机箱)生成一个rust-crypto键区：

extern crate crypto; // rust-crypto = "0.2.36"

use crypto::ed25519;
use crypto::sha2::Sha256;
use crypto::digest::Digest;

fn main() {
    let phrase = "purchase hobby popular celery evil fantasy someone party position gossip host gather";
    let mut seed = Sha256::new();
    seed.input_str(&phrase);
    let (_priv, _publ) = ed25519::keypair(&seed); // expects slice
}

但是，我完全不理解如何正确地将SHA256传递给ed25519::keypair()函数。我追踪到&seed.result_str()的结果是：

"fc37862cb425ca4368e8e368c54bb6ea0a1f305a225978564d1bdabdc7d99bdb"

这是正确的哈希，而&seed.result_str().as_bytes()的结果是：

[102, 99, 51, 55, 56, 54, 50, 99, 98, 52, 50, 53, 99, 97, 52, 51, 54, 56, 101, 56, 101, 51, 54, 56, 99, 53, 52, 98, 98, 54, 101, 97, 48, 97, 49, 102, 51, 48, 53, 97, 50, 50, 53, 57, 55, 56, 53, 54, 52, 100, 49, 98, 100, 97, 98, 100, 99, 55, 100, 57, 57, 98, 100, 98]

这是我不想要的，完全不同的东西。现在的问题主要是：

   |
36 |     let (_priv, _publ) = ed25519::keypair(&seed);
   |                                           ^^^^^ expected slice, found struct `crypto::sha2::Sha256`
   |
   = note: expected type `&[u8]`
              found type `&crypto::sha2::Sha256`

如何正确地将crypto::sha2::Sha256哈希转换为[u8]表示？

Answer 1

最初，Sha256 API可能有点混乱，因为它的设计目的是不为数据分配任何新内存。这是为了避免浪费内存分配，以防您自己分配内存。相反，您给它一个可以写入的缓冲区：

// Create a buffer in which to write the bytes, making sure it's
// big enough for the size of the hash
let mut bytes = vec![0; seed.output_bytes()];
// Write the raw bytes from the hash into the buffer
seed.result(&mut bytes);

// A reference to a Vec can be coerced to a slice
let (_priv, _publ) = ed25519::keypair(&bytes);