Permission Of Open Symmetric And Decryptbycert

I create a certificate and a symmetric key encryption by it.
Then i create a user and grant the view definition permission of both object to the user.

But it return a error message "Cannot find the certificate 'cert1', because it does not exist or you do not have permission" when execute the open symmetric sql statement as the user.

It' very surprised that it return a string when execute encryptbyCert function ,but it return null when execute decryptbyCert function...




Code Block
create certificate cert1 encryption by password='P@ssw0rd1' with subject='cert protected by self'
create symmetric key key1 with algorithm=rc2 encryption by certificate cert1
create user user1 without login
grant view definition on certificate::cert1 to user1
grant view definition on symmetric key::key1 to user1
execute as user='user1'
open symmetric key key1 decryption by certificate cert1 with password='P@ssw0rd1'--return a error
/*
Msg 15151, Level 16, State 1, Line 0
Cannot find the certificate 'cert1', because it does not exist or you do not have permission.
*/
declare @n varchar(100)
set @n='aa'
declare @c varbinary(1000)
select @c=encryptbycert(cert_id('cert1'),@n)---return a encrypt data
select convert(varchar,decryptbycert(cert_id('cert1'),@c,N'P@ssw0rd1'))--return null





any suggestions?









Thanks