Linux – squid authentication error kerberos – windows active directory

I use squid on RHEL6 and I want that authentication is via AD windows 2008, I already joined the server to the windows domain and all users is already seen by wbinfo -u wbinfo -g but wbmin -t show error below :

$ wbinfo -t
checking the trust secret for domain TELMA via RPC calls failed
Could not check secret

I followed this tuto https://www.dalemacartney.com/2012/0…nd-simple-way/ and all is fine and normally all user on domain doesn't require authentication but when I configured the browser to point to the proxy it's always requiring authentication and showing error below on /var/log/squid/cache.log :

2014/07/31 15:47:07| squid_kerb_auth: ERROR: gss_acquire_cred() failed: Unspecified GSS failure. Minor code may provide more information. Unknown error
2014/07/31 15:47:07| squid_kerb_auth: INFO: User not authenticated
2014/07/31 15:47:07| authenticateNegotiateHandleReply: Error validating user via Negotiate. Error returned 'BH gss_acquire_cred() failed: Unspecified GSS failure. Minor code may provide more information. Unknown error'

This command also provides error below :

$ kinit -V -k -t /etc/krb5.keytab
Using default cache: /tmp/krb5cc_10084_H30tfi
kinit: Cannot determine realm for host (principal host/rhel6test@)

Find below my squid.conf configuration :

auth_param negotiate program /usr/lib64/squid/squid_kerb_auth
auth_param negotiate children 10
auth_param negotiate keep_alive on

http_access deny !ad_auth
http_access allow ad_auth

Could someone help for this issue?