Struct ed25519_dalek::ExpandedSecretKey

#[repr(C)]
pub struct ExpandedSecretKey { /* fields omitted */ }

An "expanded" secret key.

This is produced by using an hash function with 512-bits output to digest a SecretKey. The output digest is then split in half, the lower half being the actual key used to sign messages, after twiddling with some bits.¹ The upper half is used a sort of half-baked, ill-designed² pseudo-domain-separation "nonce"-like thing, which is used during signature production by concatenating it with the message to be signed before the message is hashed.

Methods

impl ExpandedSecretKey

fn to_bytes(&self) -> [u8; 64]

Convert this ExpandedSecretKey into an array of 64 bytes.

Returns

An array of 64 bytes. The first 32 bytes represent the "expanded" secret key, and the last 32 bytes represent the "domain-separation" "nonce".

Examples

use rand::{Rng, OsRng};
use sha2::Sha512;
use ed25519_dalek::{SecretKey, ExpandedSecretKey};

let mut csprng: OsRng = OsRng::new().unwrap();
let secret_key: SecretKey = SecretKey::generate(&mut csprng);
let expanded_secret_key: ExpandedSecretKey = ExpandedSecretKey::from(&secret_key);
let expanded_secret_key_bytes: [u8; 64] = expanded_secret_key.to_bytes();

assert!(&expanded_secret_key_bytes[..] != &[0u8; 64][..]);

fn from_bytes(bytes: &[u8]) -> Result<ExpandedSecretKey, DecodingError>

Construct an ExpandedSecretKey from a slice of bytes.

Returns

A Result whose okay value is an EdDSA ExpandedSecretKey or whose error value is an DecodingError describing the error that occurred.

Examples

use rand::{Rng, OsRng};
use ed25519_dalek::{SecretKey, ExpandedSecretKey};
use ed25519_dalek::DecodingError;

let mut csprng: OsRng = OsRng::new().unwrap();
let secret_key: SecretKey = SecretKey::generate(&mut csprng);
let expanded_secret_key: ExpandedSecretKey = ExpandedSecretKey::from(&secret_key);
let bytes: [u8; 64] = expanded_secret_key.to_bytes();
let expanded_secret_key_again = ExpandedSecretKey::from_bytes(&bytes)?;

fn from_secret_key<D>(secret_key: &SecretKey) -> ExpandedSecretKey where
    D: Digest<OutputSize = U64> + Default, 

Construct an ExpandedSecretKey from a SecretKey, using hash function D.

Examples

use rand::{Rng, OsRng};
use sha2::Sha512;
use ed25519_dalek::{SecretKey, ExpandedSecretKey};

let mut csprng: OsRng = OsRng::new().unwrap();
let secret_key: SecretKey = SecretKey::generate(&mut csprng);
let expanded_secret_key: ExpandedSecretKey = ExpandedSecretKey::from_secret_key::<Sha512>(&secret_key);

fn sign<D>(&self, message: &[u8], public_key: &PublicKey) -> Signature where
    D: Digest<OutputSize = U64> + Default, 

Sign a message with this ExpandedSecretKey.