That's so World War I. They actually had paper code books, which needed to go down with the ship in the event of trouble.
Come World War II, the Germans and the Japanese tried to automate the process, building machines on which you could type cleartext and get ciphertext or vice-versa. However, those systems still suffered from key distribution problems and resulting operator corner-cutting and were both broken.
These days, we use public key cryptography to solve the key distribution problem. And when we need true random numbers, well, there's a device for that:
$ head -c 256 /dev/random|xxd 0000000: c0c2 e812 fdaa 4200 3608 0f8f c1d5 551a ......B.6.....U. 0000010: 435c bed8 a321 5c41 578f 7c81 7d62 f1d6 C\...!\AW.|.}b.. 0000020: 7a9f 7e5e d76c 7fc7 042f 688a 77d6 fa36 z.~^.l.../h.w..6 0000030: 33b9 b129 3ff8 8c41 1ced 0902 aef3 6989 3..)?..A......i. 0000040: d303 3dde b4e0 7de8 ac51 4467 c410 7ec2 ..=...}..QDg..~. 0000050: 2e57 b3db 87c2 06a3 5126 cd59 849a 110f .W......Q&.Y.... 0000060: f49f 6699 33e1 e7a9 a583 bd83 2afe 94b0 ..f.3.......*... 0000070: 0a3d 18cb d889 d85b da72 4892 ed46 5562 .=.....[.rH..FUb 0000080: bc9a 0be0 4b20 4ec8 fa12 b172 dc75 22d3 ....K N....r.u". 0000090: 24a1 f148 d2fa 7c85 84ab b2dc 15e9 6c43 $..H..|.......lC 00000a0: 2e07 512c 2fb0 9565 b5af 940f fcdd dec8 ..Q,/..e........ 00000b0: bc83 9f9c 9954 4989 a850 d246 1b54 27fb .....TI..P.F.T'. 00000c0: 74b2 85c0 14e9 a306 949c 6417 4281 339c t.........d.B.3. 00000d0: 7db1 178e 6e6a 585c 432c 5618 8c31 358a }...njX\C,V..15. 00000e0: 938a 649d 59d4 d7e1 dbb2 5d5d 4b6d 43d8 ..d.Y.....]]KmC. 00000f0: 888b 3721 112b ac0b 92a0 15c8 c7ea 96a3 ..7!.+..........
It all happens under the covers whenever you see the green padlock in the location bar.