I learned Kriya yoga From My Guru Shibendu Lahiri. Its a combination of Laya Yoga, Raja Yoga and Hatha Yoga. pranayama and mudra. It is one of the most powerful technique I learned among.
Its slow process and less joyful at the beginning as compared to sudarshan kriya, but its said that slow and steady wins the race. ( Please note: I am not comparing these two techniques. both techniques are superb. but benefits of both are different and the beginning only. I am only trying to put the difference between an experience. )
The below information I have collected from wiki.
Kriya Yoga (क्रिया योग) is described by its practitioners as the ancient Yoga system revived in modern times by Mahavatar Babaji through his disciple Lahiri Mahasaya, c. 1861. Kriya Yoga was brought to international awareness by Paramahansa Yogananda‘s book Autobiography of a Yogi and through Yogananda’s introductions of the practice to the west from 1920.
According to Yogananda the ancient Yogic text the Yoga Sutras of Patanjali, contains a description of Kriya Yoga in the second chapter II.49: “Liberation can be attained by that pranayama which is accomplished by disjoining the course of inspiration and expiration.”
The Kriya yoga system consists of a number of levels of pranayama, mantra, and mudra based on techniques intended to rapidly accelerate spiritual development and engender a profound state of tranquility and God-communion. Yogananda attributes his description of Kriya Yoga to his lineage of gurus, Sri Yukteswar Giri, Lahiri Mahasaya, and Mahavatar Babaji (fl. 1860s). The latter is reported to have introduced the concept as essentially identical to the Raja Yoga of Patanjali and the concept of Yoga as described in the Bhagavad Gita.
Kriya Yoga, as taught by Lahiri Mahasaya, is traditionally exclusively learned via the Guru-disciple relationship and the initiation consists of a secret ceremony. He recounted that after his initiation into Kriya Yoga, “Babaji instructed me in the ancient rigid rules which govern the transmission of the yogic art from Guru to disciple.”
As Yogananda describes Kriya Yoga, “The Kriya Yogi mentally directs his life energy to revolve, upward and downward, around the six spinal centers (medullary, cervical, dorsal, lumbar, sacral, and coccygeal plexuses) which correspond to the twelve astral signs of the zodiac, the symbolic Cosmic Man. One half-minute of revolution of energy around the sensitive spinal cord of man effects subtle progress in his evolution; that half-minute of Kriya equals one year of natural spiritual unfoldment.”