with certificates and the privacy of data exchanged with strong ciphers.

When negotiating a connection to an HTTPS server, OkHttp needs to know which [TLS versions](https://square.github.io/okhttp/4.x/okhttp/okhttp3/-tls-version/) and [cipher suites](https://square.github.io/okhttp/4.x/okhttp/okhttp3/-cipher-suite/) to offer. A client that wants to maximize connectivity would include obsolete TLS versions and weak-by-design cipher suites. A strict client that wants to maximize security would...

    }

    @Test
    @DisplayName("Should handle different cipher IDs")
    void testDifferentCipherIds() {
        // Test cipher ID 1 (AES-CCM)
        Smb2EncryptionContext context1 = new Smb2EncryptionContext(1, DialectVersion.SMB311, testEncryptionKey, testDecryptionKey);
        assertEquals(1, context1.getCipherId(), "Should handle cipher ID 1");

        // Test cipher ID 2 (AES-GCM)

    @Test
    @DisplayName("Should return selected cipher")
    void testGetSelectedCipher() throws Exception {
        // Given
        setPrivateField(response, "selectedCipher", EncryptionNegotiateContext.CIPHER_AES128_GCM);

        // When
        int cipher = response.getSelectedCipher();

        // Then
        assertEquals(EncryptionNegotiateContext.CIPHER_AES128_GCM, cipher);
    }

    @Test

        };
        roleQueryHelperImpl.cipher = cipher;

        Set<String> roleSet;
        boolean encrypted;
        String value;

        encrypted = true;
        value = cipher.encryptoText("");
        roleSet = decodedRoleList(roleQueryHelperImpl, value, encrypted);
        assertEquals(0, roleSet.size());

        encrypted = true;
        value = cipher.encryptoText("role1");

---

<a name="tlsv13_only"></a>
#### ¹ TLSv1.3 Only

Cipher suites that are only available with TLSv1.3.

<a name="http2_naughty"></a>
#### ² HTTP/2 Cipher Suite Denylist

Cipher suites that are [discouraged for use][http2_denylist] with HTTP/2. OkHttp includes them because better suites are not commonly available. For example, none of the better cipher suites listed above shipped with Android 4.4 or Java 7.

        byte[] keybytes = key.getEncoded();
        Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
        cipher.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(keybytes, "AES"), new IvParameterSpec(ZERO_IV, 0, ZERO_IV.length));
        if (constant.length != cipher.getBlockSize()) {
            constant = expandNFold(constant, cipher.getBlockSize());
        }
        byte[] enc = constant;

        return new HMACT64(key);
    }

    /**
     * Get an RC4 cipher instance initialized with the specified key.
     * @param key the encryption key
     * @return RC4 cipher in encryption mode
     */
    public static Cipher getArcfour(final byte[] key) {
        try {
            final Cipher c = Cipher.getInstance("RC4");
            c.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(key, "RC4"));
            return c;

import okhttp3.FallbackTestClientSocketFactory.Companion.TLS_FALLBACK_SCSV

/**
 * An SSLSocketFactory that delegates calls. Sockets created by the delegate are wrapped with ones
 * that will not accept the [TLS_FALLBACK_SCSV] cipher, thus bypassing server-side fallback
 * checks on platforms that support it. Unfortunately this wrapping will disable any
 * reflection-based calls to SSLSocket from Platform.
 */
class FallbackTestClientSocketFactory(

        SecretKeySpec dataKey = new SecretKeySpec(dataHmac, KerberosConstants.RC4_ALGORITHM);

        cipher = Cipher.getInstance(KerberosConstants.RC4_ALGORITHM);
        cipher.init(Cipher.DECRYPT_MODE, dataKey);

        int plainDataLength = data.length - KerberosConstants.CHECKSUM_SIZE;
        byte[] plainData = cipher.doFinal(data, KerberosConstants.CHECKSUM_SIZE, plainDataLength);

        IvParameterSpec ivSpec = new IvParameterSpec(iv);

        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        cipher.init(Cipher.ENCRYPT_MODE, keySpec, ivSpec);
        byte[] encrypted = cipher.doFinal(plaintext);

        cipher.init(Cipher.DECRYPT_MODE, keySpec, ivSpec);
        byte[] decrypted = cipher.doFinal(encrypted);

        // Then
        assertNotNull(encrypted);