Rust

DSA Signature Create and Verify

See more DSA Examples

Shows how to create a DSA (DSS) signature for the contents of a file. The first step is to create an SHA-1 hash of the file contents. The hash is signed using the Digital Signature Algorithm and the signature bytes are retrieved as a hex-encoded string.

The 2nd part of the example loads the signature and verifies it against the hash.

Rust

let mut success = false;

// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

let crypt = chilkat::Crypt2::new();

crypt.set_encoding_mode("hex");
crypt.set_hash_algorithm("sha-1");

// Return the SHA-1 hash of a file.  The file may be any size.
// The Chilkat Crypt component will stream the file when 
// computing the hash, keeping the memory usage constant
// and reasonable.
// The 20-byte SHA-1 hash is returned as a hex-encoded string.
let hash_str = crypt.hash_file_enc("hamlet.xml").unwrap_or_default();

let dsa = chilkat::Dsa::new();

// Load a DSA private key from a PEM file.  Chilkat DSA
// provides the ability to load and save DSA public and private
// keys from encrypted or non-encrypted PEM or DER.
// The LoadText method is for convenience only.  You may
// use any means to load the contents of a PEM file into
// a string.
let pem_private_key = dsa.load_text("dsa_priv.pem").unwrap_or_default();
if dsa.from_pem(&pem_private_key).is_err() {
    println!("{}", dsa.last_error_text());
    return;
}

// You may optionally verify the key to ensure that it is a valid
// DSA key.
success = dsa.verify_key();
if !success {
    println!("{}", dsa.last_error_text());
    return;
}

// Load the hash to be signed into the DSA object:
if dsa.set_encoded_hash("hex", &hash_str).is_err() {
    println!("{}", dsa.last_error_text());
    return;
}

// Now that the DSA object contains both the private key and hash,
// it is ready to create the signature:
if dsa.sign_hash().is_err() {
    println!("{}", dsa.last_error_text());
    return;
}

// If SignHash is successful, the DSA object contains the
// signature.  It may be accessed as a hex or base64 encoded
// string.  (It is also possible to access directly in byte array form via
// the "Signature" property.)
let hex_sig = dsa.get_encoded_signature("hex").unwrap_or_default();
println!("Signature:");
println!("{}", hex_sig);

// -----------------------------------------------------------
// Step 2: Verify the DSA Signature
// -----------------------------------------------------------

let dsa2 = chilkat::Dsa::new();

// Load the DSA public key to be used for verification:
let pem_public_key = dsa2.load_text("dsa_pub.pem").unwrap_or_default();
if dsa2.from_public_pem(&pem_public_key).is_err() {
    println!("{}", dsa2.last_error_text());
    return;
}

// Load the hash to be verified against the signature.
if dsa2.set_encoded_hash("hex", &hash_str).is_err() {
    println!("{}", dsa2.last_error_text());
    return;
}

// Load the signature:
if dsa2.set_encoded_signature("hex", &hex_sig).is_err() {
    println!("{}", dsa2.last_error_text());
    return;
}

// Verify:
if dsa2.verify().is_err() {
    println!("{}", dsa2.last_error_text());
} else {
    println!("DSA Signature Verified!");
}