RSA can work with keys of different keys of length: 1024, 2048, 3072, 4096, 8129, 16384 or even more bits. Key length of 3072-bits and above are considered secure. Longer keys provide higher security but consume more computing time, so there is a tradeoff between security and speed. Very long RSA keys (e.g. 50000 bits or 65536 bits) may be too slow for practical use, e.g. key generation may take from several minutes to several hours.