If the length of the key is lengthened, the decipherment becomes difficult. However, when the key is long, the calculation cost of the key generation, the encryption, and the decryption grows this time. Therefore, the RSA code shoulders the fate that it keeps operating it while the balance of a calculation cost and necessary code strength. Also it was in consideration of DVD player's limited processing performance though it was assumed as one cause the length of the key 40 bits and short that the code of DVD had been broken though the encryption was different from RSA.
Idea that arose from chance meeting
The common sense of such encryption technology use was broken, and a quite new
"The encryption that we developed has been proven that the decipherment is
mathematically impossible. "