Using AES-256 Encryption

If you are using CentOS/Red Hat Enterprise Linux 5.6 or higher, or Ubuntu, which use AES-256 encryption by default for tickets, you must install the Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy File on all cluster and Hadoop user machines. For JCE Policy File installation instructions, see the README.txt file included in the jce_policy-x.zip file. For more information, see Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy File

Alternately, you can configure Kerberos to not use AES-256 by removing aes256-cts:normal from the supported_enctypes field of the kdc.conf or krb5.conf file. After changing the kdc.conf file, you must restart both the KDC and the kadmin server for those changes to take affect. You may also need to re-create or change the password of the relevant principals, including, potentially the Ticket Granting Ticket principal (krbtgt/REALM@REALM). If AES-256 is still used after completing steps, the aes256-cts:normal setting existed when the Kerberos database was created. To fix this, create a new Kerberos database and then restart both the KDC and the kadmin server.

To verify the type of encryption used in your cluster:

On the local KDC host, type this command to create a test principal:
```
kadmin -q "addprinc test" 
```
On a cluster host, type this command to start a Kerberos session as the test principal:
```
kinit test 
```

On a cluster host, type this command to view the encryption type in use:

klist -e

If AES is being used, output like the following is displayed after you type the klist command; note that AES-256 is included in the output:

Ticket cache: FILE:/tmp/krb5cc_0
Default principal: test@SCM
Valid starting     Expires            Service principal
05/19/11 13:25:04  05/20/11 13:25:04  krbtgt/SCM@SCM
    Etype (skey, tkt): AES-256 CTS mode with 96-bit SHA-1 HMAC, AES-256 CTS mode with 96-bit SHA-1 HMAC