英文:
How to regenerate private key using EdDSA/Ed448 signature algorithm?
问题
这是我生成密钥对的方式:
var keyPairGenerator = KeyPairGenerator.getInstance("Ed448");
keyPairGenerator.initialize(448, SecureRandom.getInstanceStrong());
var keyPair = keyPairGenerator.generateKeyPair();
var privateKey = keyPair.getPrivate();
var publicKey = keyPair.getPublic();
byte[] privateKeyBytes = privateKey.getEncoded();
byte[] publicKeyBytes = publicKey.getEncoded();
然而,当我尝试再次生成密钥时,出现了异常:
var keyFactory = KeyFactory.getInstance("EdDSA");
var edECPoint = byteArrayToEdPoint(publicKeyBytes);
var edECPublicKeySpec = new EdECPublicKeySpec(new NamedParameterSpec("Ed448"), edECPoint);
var publicKey = keyFactory.generatePublic(edECPublicKeySpec);
var edECPrivateKeySpec = new EdECPrivateKeySpec(new NamedParameterSpec("Ed448"), privateKeyBytes);
var privateKey = keyFactory.generatePrivate(edECPrivateKeySpec); // generatePrivate() 抛出异常
异常堆栈跟踪:
Exception in thread "main" java.security.spec.InvalidKeySpecException: java.security.InvalidKeyException: key length is 73, key length must be 57
at jdk.crypto.ec/sun.security.ec.ed.EdDSAKeyFactory.engineGeneratePrivate(EdDSAKeyFactory.java:129)
at java.base/java.security.KeyFactory.generatePrivate(KeyFactory.java:390)
at io.fouad.Main.main(Main.java:48)
Caused by: java.security.InvalidKeyException: key length is 73, key length must be 57
at jdk.crypto.ec/sun.security.ec.ed.EdDSAPrivateKeyImpl.checkLength(EdDSAPrivateKeyImpl.java:84)
at jdk.crypto.ec/sun.security.ec.ed.EdDSAPrivateKeyImpl.<init>(EdDSAPrivateKeyImpl.java:61)
at jdk.crypto.ec/sun.security.ec.ed.EdDSAKeyFactory.generatePrivateImpl(EdDSAKeyFactory.java:171)
at jdk.crypto.ec/sun.security.ec.ed.EdDSAKeyFactory.engineGeneratePrivate(EdDSAKeyFactory.java:127)
... 2 more
这里是我从 OpenJDK 仓库 复制的一些实用程序:
private static EdECPoint byteArrayToEdPoint(byte[] arr)
{
byte msb = arr[arr.length - 1];
boolean xOdd = (msb & 0x80) != 0;
arr[arr.length - 1] &= (byte) 0x7F;
reverse(arr);
BigInteger y = new BigInteger(1, arr);
return new EdECPoint(xOdd, y);
}
private static void reverse(byte [] arr)
{
int i = 0;
int j = arr.length - 1;
while(i < j)
{
swap(arr, i, j);
i++;
j--;
}
}
private static void swap(byte[] arr, int i, int j)
{
byte tmp = arr[i];
arr[i] = arr[j];
arr[j] = tmp;
}
英文:
Here is how I generated the key pair:
var keyPairGenerator = KeyPairGenerator.getInstance("Ed448");
keyPairGenerator.initialize(448, SecureRandom.getInstanceStrong());
var keyPair = keyPairGenerator.generateKeyPair();
var privateKey = keyPair.getPrivate();
var publicKey = keyPair.getPublic();
byte[] privateKeyBytes = privateKey.getEncoded();
byte[] publicKeyBytes = publicKey.getEncoded();
However, when I tried to regenerate the keys again, I got an exception:
var keyFactory = KeyFactory.getInstance("EdDSA");
var edECPoint = byteArrayToEdPoint(publicKeyBytes);
var edECPublicKeySpec = new EdECPublicKeySpec(new NamedParameterSpec("Ed448"), edECPoint);
var publicKey = keyFactory.generatePublic(edECPublicKeySpec);
var edECPrivateKeySpec = new EdECPrivateKeySpec(new NamedParameterSpec("Ed448"), privateKeyBytes);
var privateKey = keyFactory.generatePrivate(edECPrivateKeySpec); // generatePrivate() throws exception
The exception stacktrace:
Exception in thread "main" java.security.spec.InvalidKeySpecException: java.security.InvalidKeyException: key length is 73, key length must be 57
at jdk.crypto.ec/sun.security.ec.ed.EdDSAKeyFactory.engineGeneratePrivate(EdDSAKeyFactory.java:129)
at java.base/java.security.KeyFactory.generatePrivate(KeyFactory.java:390)
at io.fouad.Main.main(Main.java:48)
Caused by: java.security.InvalidKeyException: key length is 73, key length must be 57
at jdk.crypto.ec/sun.security.ec.ed.EdDSAPrivateKeyImpl.checkLength(EdDSAPrivateKeyImpl.java:84)
at jdk.crypto.ec/sun.security.ec.ed.EdDSAPrivateKeyImpl.<init>(EdDSAPrivateKeyImpl.java:61)
at jdk.crypto.ec/sun.security.ec.ed.EdDSAKeyFactory.generatePrivateImpl(EdDSAKeyFactory.java:171)
at jdk.crypto.ec/sun.security.ec.ed.EdDSAKeyFactory.engineGeneratePrivate(EdDSAKeyFactory.java:127)
... 2 more
and here is some utilities I copied from OpenJDK repo:
private static EdECPoint byteArrayToEdPoint(byte[] arr)
{
byte msb = arr[arr.length - 1];
boolean xOdd = (msb & 0x80) != 0;
arr[arr.length - 1] &= (byte) 0x7F;
reverse(arr);
BigInteger y = new BigInteger(1, arr);
return new EdECPoint(xOdd, y);
}
private static void reverse(byte [] arr)
{
int i = 0;
int j = arr.length - 1;
while(i < j)
{
swap(arr, i, j);
i++;
j--;
}
}
private static void swap(byte[] arr, int i, int j)
{
byte tmp = arr[i];
arr[i] = arr[j];
arr[j] = tmp;
}
答案1
得分: 4
// 获取私钥的编码(实例将是`EdDSAPrivateKeyImpl`类型),将返回PKCS8格式的密钥,因此您应该使用`PKCS8EncodedKeySpec`:
var keyFactory = KeyFactory.getInstance("EdDSA");
var pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(privateKeyBytes);
var privateKey = keyFactory.generatePrivate(pkcs8EncodedKeySpec);
// 否则,您将不得不自己解包序列,并按照[RFC5958-section2](https://www.rfc-editor.org/rfc/rfc5958#section-2)中描述的方法获取`PrivateKey`(这是OctetString)。然后您可以使用`EdECPrivateKeySpec`。
英文:
Since privateKey.getEncoded
(the instance will be of EdDSAPrivateKeyImpl
type) will return a key in PKCS8 format, you should use PKCS8EncodedKeySpec
:
var keyFactory = KeyFactory.getInstance("EdDSA");
var pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(privateKeyBytes);
var privateKey = keyFactory.generatePrivate(pkcs8EncodedKeySpec);
Otherwise you would have to unwrap the the sequence yourself and get PrivateKey
(this is OctetString) as described in RFC5958-section2. Then you could use EdECPrivateKeySpec
.
答案2
得分: 1
方法 #1:
var keyPairGenerator = KeyPairGenerator.getInstance("Ed25519");
var keyPair = keyPairGenerator.generateKeyPair();
var privateKey = (EdECPrivateKey) keyPair.getPrivate();
var publicKey = (EdECPublicKey) keyPair.getPublic();
byte[] privateKeyBytes = privateKey.getBytes().orElseThrow();
var edecPoint = publicKey.getPoint();
BigInteger y = edecPoint.getY();
boolean xOdd = edecPoint.isXOdd();
// 使用 (privateKeyBytes)、(y) 和 (xOdd) 重构密钥
var keyFactory = KeyFactory.getInstance("Ed25519");
var edECPublicKeySpec = new EdECPublicKeySpec(NamedParameterSpec.ED25519, new EdECPoint(xOdd, y));
var publicKey2 = keyFactory.generatePublic(edECPublicKeySpec);
var edECPrivateKeySpec = new EdECPrivateKeySpec(NamedParameterSpec.ED25519, privateKeyBytes);
var privateKey2 = keyFactory.generatePrivate(edECPrivateKeySpec);
方法 #2:
var keyPairGenerator = KeyPairGenerator.getInstance("Ed25519");
var keyPair = keyPairGenerator.generateKeyPair();
var privateKey = keyPair.getPrivate();
var publicKey = keyPair.getPublic();
byte[] privateKeyBytes = privateKey.getEncoded();
byte[] publicKeyBytes = publicKey.getEncoded();
// 使用 (privateKeyBytes) 和 (publicKeyBytes) 重构密钥
var keyFactory = KeyFactory.getInstance("Ed25519");
var publicKey2 = keyFactory.generatePublic(new X509EncodedKeySpec(publicKeyBytes));
var privateKey2 = keyFactory.generatePrivate(new PKCS8EncodedKeySpec(privateKeyBytes));
英文:
Method #1:
var keyPairGenerator = KeyPairGenerator.getInstance("Ed25519");
var keyPair = keyPairGenerator.generateKeyPair();
var privateKey = (EdECPrivateKey) keyPair.getPrivate();
var publicKey = (EdECPublicKey) keyPair.getPublic();
byte[] privateKeyBytes = privateKey.getBytes().orElseThrow();
var edecPoint = publicKey.getPoint();
BigInteger y = edecPoint.getY();
boolean xOdd = edecPoint.isXOdd();
// reconstruct the keys using (privateKeyBytes), (y) and (xOdd)
var keyFactory = KeyFactory.getInstance("Ed25519");
var edECPublicKeySpec = new EdECPublicKeySpec(NamedParameterSpec.ED25519, new EdECPoint(xOdd, y));
var publicKey2 = keyFactory.generatePublic(edECPublicKeySpec);
var edECPrivateKeySpec = new EdECPrivateKeySpec(NamedParameterSpec.ED25519, privateKeyBytes);
var privateKey2 = keyFactory.generatePrivate(edECPrivateKeySpec);
Method #2:
var keyPairGenerator = KeyPairGenerator.getInstance("Ed25519");
var keyPair = keyPairGenerator.generateKeyPair();
var privateKey = keyPair.getPrivate();
var publicKey = keyPair.getPublic();
byte[] privateKeyBytes = privateKey.getEncoded();
byte[] publicKeyBytes = publicKey.getEncoded();
// reconstruct the keys using (privateKeyBytes) and (publicKeyBytes)
var keyFactory = KeyFactory.getInstance("Ed25519");
var publicKey2 = keyFactory.generatePublic(new X509EncodedKeySpec(publicKeyBytes));
var privateKey2 = keyFactory.generatePrivate(new PKCS8EncodedKeySpec(privateKeyBytes));
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