Kriya yoga is a science about which we have ample references in the tantra shastras. The practices of traditional kriya yoga are a combination of pranayama, mudra, bandha and dhyana .It is called kriyas because every movement, every action is taking place within you, not outside you. Originally these kriyas were forming a part of tantra. Tantra was abused and misused. People did not even want to know it. So the wise people thought it was much better to take out the useful portion, and so they took out kriya yoga from tantra.

For every yoga, raja yoga disciplines must be practised like satya , ahimsa, brahmacharya. 

For a householder it is not possible to practise everything. If he practises these he is not a grihastha (householder ) .Maybe there are some householders who could, but most cannot. There are certain things in grihastha ashrama which are very necessary to experience life. The relationship between husband and wife is a natural relationship, it is necessary for your physical, mental, emotional and spiritual progress. Therefore, if you force yourself to practise brahmacharya you might even become sick. The rishis thought, ‘What is the way?’ They gradually came to the conclusion that tantra is the way. In tantra, the ordinary behaviour of the grihastha ashrama is acceptable. Like vishaya bhoga, sensual gratification, dukha , pain, sentiment, love, passion, greed they are called ordinary behaviour. These ordinary behaviours are acceptable in tantra.Tantra marga says that whatever you are in the grihastha ashrama (householder) whether you are a sattwic, rajasic or a tamasic , it does not matter. You practise kriya yoga. When you practise kriya yoga for a few months , what will happen? If you are a tamasic , you will progress and become a rajasic. If you are a rajasic you will make improvement and progress, you will become a sattwic. When you become a sattwic, the awakening will happen . Therefore, tantra says do not wait until you become sattwic. If you wait for nature to make you sattwic, it will take you births after births. So practise kriya yoga and transform yourself from tamas to rajas and from rajas to sattwa …

( as received from a reliable source )