Apex Guid generator

ContactGuidGenerator

trigger ContactGuidGenerator on Contact (before insert) {
    for( Contact c: Trigger.new ) {
        Blob b = Crypto.GenerateAESKey(128);
        String h = EncodingUtil.ConvertTohex(b);
        String guid = h.SubString(0,8)+ h.SubString(8,12) + h.SubString(12,16) + h.SubString(16,20) + h.substring(20);
        c.guid__c = guid;
        // guid should be Text, size 32
    }       
}