java.lang.Object
- org.asynchttpclient.scram.ScramEngine

```
public final class ScramEngine
extends Object
```
Core SCRAM-SHA-256 cryptographic operations (RFC 5802, RFC 7804). Thread-safe: all methods are stateless.

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method	Description
`static byte[]`	`computeClientKey(byte[] saltedPassword)`	ClientKey := HMAC(SaltedPassword, "Client Key")
`static byte[]`	`computeClientProof(byte[] clientKey, byte[] clientSignature)`	ClientProof := ClientKey XOR ClientSignature
`static byte[]`	`computeClientSignature(byte[] storedKey, String authMessage)`	ClientSignature := HMAC(StoredKey, AuthMessage)
`static byte[]`	`computeSaltedPassword(String password, byte[] salt, int iterations)`	SaltedPassword := Hi(Normalize(password), salt, i)
`static byte[]`	`computeServerKey(byte[] saltedPassword)`	ServerKey := HMAC(SaltedPassword, "Server Key")
`static byte[]`	`computeServerSignature(byte[] serverKey, String authMessage)`	ServerSignature := HMAC(ServerKey, AuthMessage)
`static byte[]`	`computeStoredKey(byte[] clientKey)`	StoredKey := H(ClientKey)
`static String`	`generateNonce(int lengthBytes)`	Generate a cryptographically random nonce, base64-encoded.
`static byte[]`	`hash(byte[] data)`	Compute SHA-256 hash.
`static byte[]`	`hi(String normalizedPassword, byte[] salt, int iterations)`	PBKDF2 / Hi() computation as defined in RFC 5802.
`static byte[]`	`hmac(byte[] key, byte[] data)`	Compute HMAC-SHA-256.
`static String`	`normalizePassword(String password)`	Normalize password per RFC 7613 OpaqueString profile.
`static byte[]`	`xor(byte[] a, byte[] b)`	XOR two equal-length byte arrays.
`static void`	`zeroBytes(byte[] array)`	Zero out a byte array for security.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

hi
```
public static byte[] hi(String normalizedPassword,
                        byte[] salt,
                        int iterations)
```
PBKDF2 / Hi() computation as defined in RFC 5802. Hi(str, salt, i) = PBKDF2(str, salt, i, dkLen)

Parameters:

normalizedPassword - the normalized password (String, UTF-8 encoded internally)

salt - the salt bytes

iterations - the iteration count

Returns:

the derived key bytes

hmac

public static byte[] hmac(byte[] key,
                          byte[] data)

Compute HMAC-SHA-256.

hash

public static byte[] hash(byte[] data)

Compute SHA-256 hash.

xor

public static byte[] xor(byte[] a,
                         byte[] b)

XOR two equal-length byte arrays. Mutates array a in-place.

generateNonce
```
public static String generateNonce(int lengthBytes)
```
Generate a cryptographically random nonce, base64-encoded.

Parameters:

lengthBytes - number of random bytes (before base64 encoding)

Returns:

base64-encoded nonce string

normalizePassword
```
public static String normalizePassword(String password)
```
Normalize password per RFC 7613 OpaqueString profile. Steps applied in order: 1) width mapping (preserve), 2) non-ASCII spaces to U+0020, 3) case preserved, 4) NFC normalization, 5) prohibited char check.

computeSaltedPassword

public static byte[] computeSaltedPassword(String password,
                                           byte[] salt,
                                           int iterations)

SaltedPassword := Hi(Normalize(password), salt, i)

computeClientKey

public static byte[] computeClientKey(byte[] saltedPassword)

ClientKey := HMAC(SaltedPassword, "Client Key")

computeStoredKey

public static byte[] computeStoredKey(byte[] clientKey)

StoredKey := H(ClientKey)

computeServerKey

public static byte[] computeServerKey(byte[] saltedPassword)

ServerKey := HMAC(SaltedPassword, "Server Key")

computeClientSignature

public static byte[] computeClientSignature(byte[] storedKey,
                                            String authMessage)

ClientSignature := HMAC(StoredKey, AuthMessage)

computeClientProof

public static byte[] computeClientProof(byte[] clientKey,
                                        byte[] clientSignature)

ClientProof := ClientKey XOR ClientSignature

computeServerSignature

public static byte[] computeServerSignature(byte[] serverKey,
                                            String authMessage)

ServerSignature := HMAC(ServerKey, AuthMessage)

zeroBytes

public static void zeroBytes(byte[] array)

Zero out a byte array for security.

Class ScramEngine