Did the company demand original certificates to be submitted by you and also did it issue any acknowledgment?
Did the company declare in job advt., interview call letter, selection letter, offer letter, appointment letter that you shall need to sign a Bond?
Do you have copy of the BOND?
The company has asked to sign BOND in lieu of what extra ordinary favor it has made to you e.g. some certified training from Instt……………………?
Does it provide salary on time with salary slip, PF number, ESIC card, etc…………..?
Are you a probationer or confirmed employee?
Are you a member of Employee’s/Tarde unions?
Why do you want to leave?
The original certificates can not be retained by company, it is your property and company can not have any lien on it.
In the meantime you may go thru the attachments and consult elders in the family and a competent and experienced Labor Consultant/Service Lawyer alongwith all docs on record and elders of the family.