如何将 crypto::sha2::Sha256 散列转换为 &[u8] 表示？

Question

我目前正在尝试从 SHA256 哈希生成 ED25519 密钥对（通过 rust-crypto crate）：

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，我完全不明白如何将 SHA256 正确传递给 ed25519::keypair() 函数。我追踪到 &seed.result_str() 结果是：

"fc37862cb425ca4368e8e368c54bb6ea0a1f305a225978564d1bdabdc7d99bdb"

这是正确的散列，而 &seed.result_str().as_bytes() 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。现在问题分解为：

   |
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 散列转换为 [u8] 表示形式？

Answer 1

Sha256 API 一开始可能有点混乱，因为它的设计使其不会为数据分配任何新内存。这是为了避免浪费内存分配，以防你想自己分配它。相反，你给它一个缓冲区来写入：

// 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);

如何将 crypto::sha2::Sha256 散列转换为 &[u8] 表示？

How to convert a crypto::sha2::Sha256 hash into a &[u8] representation?

sha

sha256

rust