DROP SIGNATURE (Transact-SQL)

module_name

Is the name of a stored procedure, function, assembly, or trigger.

CERTIFICATE cert_name

Is the name of a certificate with which the stored procedure, function, assembly, or trigger is signed.

ASYMMETRIC KEY Asym_key_name

Is the name of an asymmetric key with which the stored procedure, function, assembly, or trigger is signed.

Information about signatures is visible in the sys.crypt_properties catalog view.

Requires ALTER permission on the object and CONTROL permission on the certificate or asymmetric key. If an associated private key is protected by a password, the user also must have the password.

The following example removes the signature of certificate HumanResourcesDP from the stored procedure HumanResources.uspUpdateEmployeeLogin.

USE AdventureWorks2012;
DROP SIGNATURE FROM HumanResources.uspUpdateEmployeeLogin 
    BY CERTIFICATE HumanResourcesDP;
GO

Reference