Is submission of undated blank cheques as a security deposit safe

I have got an offer from a private company. In the agreement they have written that during the firsth 3 months of training if I leave the job then I need to pay my training expenses + (number of months * salary per month). After that if I leave during probation period i.e next 6 months then I need to pay 12*probation period salary. After that if I resign without giving 6 months' notice then I need to pay 6*salary per month. Otherwise after 9 months I can leave without paying anything( if I serve the complete notice period) and after 3 years my, they have mentioned the date, the bond will be finished and I can resign any day. Now they are asking for two undated cheques. Though in agreement they haven't written whether it should be blank or filled, but I came to know from some of the employees of that company that they take two blank cheques enclosed with the agreement. Now I want to ask that giving two undated blank cheques, how safe is that from my side? I asked some of the ex-employee