Kev muab tawm los ntawm phau ntawv ua haujlwm yog tsim los ntawm cov neeg ua haujlwm ntawm cov koom haum pabcuam kev ua haujlwm raws li sau ntawv thov los ntawm tus neeg ua haujlwm hauv peb hnub ua haujlwm. Cov lus no yog muaj nyob rau hauv Daim Duab. 62 ntawm Txoj Cai Kev Ua Haujlwm ntawm Lavxias Lavxias, nrog rau kab lus 7 ntawm Cov Kev Cai rau kev tswj thiab khaws cia cov ntawv ua haujlwm, ua cov ntawv ua haujlwm thiab muab cov chaw ua haujlwm nrog rau lawv, pom zoo los ntawm tsoomfwv ntawm Lavxias Lavxias hnub tim 04.16.2003 No. 225 "Rau ntawm phau ntawv ua haujlwm".
Cov ntaub ntawv rho tawm yog kos rau ntawm lub taub ntawv ntawm lub koom haum, yog tias muaj ib qho, thiab yuav tsum muaj ntawv pov thawj los ntawm kev kos npe ntawm lub taub hau, nrog rau lub foob lub koom haum. Cov ntawv rho tawm yuav tsum muaj cov ncauj lus qhia hauv nplooj npe, thiab raws li hauv seem "Cov ntaub ntawv hais txog kev ua haujlwm" thiab "Cov ntaub ntawv hais txog kev muab khoom plig". Kev rho tawm los ntawm phau ntawv ua haujlwm tau muab rau cov neeg ua haujlwm pub dawb.
Thaum muab ntawv pov thawj kev ua kom tiav nrog cov ntawv sau nrog tus thawj ntawm phau ntawv ua haujlwm, hauv qab no tsim nyog "Kos Npe", ib daim ntawv pov thawj muab ntawv pov thawj yog muab tso cia, suav nrog cov hauv qab no: cov ntawv sau "Tseeb"; txoj haujlwm ntawm tus neeg muab ntawv pov thawj; tus kheej kos npe ntawm tus neeg muaj ntawv pov thawj; decryption ntawm lub npe (npe, npe menyuam yaus); hnub tim lav. Lub koom haum yuav siv cov ntawv foob tshwj xeeb nrog cov ntawv sau “Kho Tawm. Cov Kws Tshuaj Xyuas Tib Neeg _ "lossis lwm cov ntawv zoo sib xws. Tab sis txawm hais tias muaj kev foob, qhov kos npe ntawm tus neeg pov thawj yuav tsum tau su los ntawm tes. Lub foob thiab kos npe ntawm tus neeg raug tso cai yog cov pov thawj ntawm qhov tseeb ntawm cov khoom tawm los ntawm phau ntawv ua haujlwm. Cov ntaub ntawv tseem muaj hnub tim ntawm qhov teeb meem thiab ib daim ntawv sau cia ua cov ntawv tseem nyob hauv cov tuam txhab, chaw haujlwm.
