Part I
Crypting Protocol

We will crypt a simple message containing the word ’salut’.

In a first step we have to compute the weight list of the differents caracters (meaning an approximation of the ASCII code used in the computer code algorithm).

Weigth List

Giving 0 to ’a’ to 26 to ’z’, we have : 18.0.11.20.19 as the weigth list of the string

Cumulated weigth list

Once done, we have to compute the cumulated weigth list. I mean, the list application can be considered as a suit defined by :

un a suit from N to N with the length n N | ui=ui-2+ui-1

In our case, the computed list is 18.18.29.49.68 We call it vi

Key Computing

At this moment we have to compute the public key ki of the algorithm defined via modulo since the formula :

{
 ki = [ui.un- i mod   26]+ 10      if  ∃ui,un-i
  uj                           if  !∃uj,j = n∕2 +1 .
(1)

With our example, it gives :

(
{ k0 = [18.19 mod   26]+10 = 14
  k1 = [20.0 mod   26]+ 10 = 10 .
( k2 = [11 mod  26]+ 10 = 11
(2)

We build the full Length key ξ  using the formula :

{
  ξi = ki     if  i <= n∕2 +1  .
  ξi = kn-i     if  i > n∕2+ 1
(3)

Crypting Process

The crypting process is ruled by a pseudo-convolution with the given symbol * meaning a point by point multiplication. This newer suit is ruled by vi and ui We call it wi defined by : vi * ui

In our example, it gives :

(|w0 = v0.u0 = 324
|||{w1 = v1.u1 = 0
 w2 = v2.u2 = 319 .
|||w3 = v3.u3 = 980
|(w4 = v5.u4 = 1292
(4)

We obtain the suit w=324.0.319.980.1292

Encryption

At the end we use the Encryption into differents numeric bases to hide the crypting process.

The Base indexes are defined by the key ξ
The list to encrypt is defined by w
The Encryption process will be caled Ξ
Defined by :

Ξi = (wi)ξi
(5)

(| Ξ = (w )  = (324) =  192
|||{ Ξ0= (w0)ξ0= (0) 14= 0
  Ξ1= (w1)ξ1= (31109) =  270  .
||| Ξ2= (w2)ξ2= (9801)1=  980
|( Ξ3= (w3)ξ3= (129120) = 684
   4    4 ξ4       14
(6)

The Encrypted suit is Ξ  = 192.0.270.980.684

Its associate key is ξ  = 14.10.11.10.14

Part II
Decrypting Protocol

Initialisation

In this demonstration, we will use a Encrypted list using the Raptor cryptographic algorithm. The terms list is given by :

!018kh”05a3c#8064$12vj%2gai&0605a(67500)0ba30*277a4+25376,2a5db-58133˙
6u7!146367”27706#1j68c

The associated key is given as a public key :

2116103428141013

We consider in a first time differents type of caracters set used in the crypting and Encrypting processes.

§= [!,”,#,$,%,&,(,),*,+,-,˙]

Using this informations, we could get a first Terms list to treat called Ξ.

018kh.05a3c.8064.12vj.2gai.0605a.67500.0ba30.277a4.25376.2a5db.5813.36u7.146367.27706.1j68c

A list with length 16 is highlighting We will use the Set X = [a-z]  [0-9]

With χ the length of the Terms list.

Here χ  = 16, we could observ than length of key ρ | ρ = χ.

Ξi will represent the respectives terms of the list.

We start the decrypting process by exctracting the key’s Bases index from the cn number suit contained in key. with ci, i [0,ρ  ], ci 9

We obtain : ξ = 21.16.10.34.28.14.10.13

Successive Base Transpositions - Step 1

Highlighted ξj , Bases index are consistent with the Terms of the suit Ξ

Thereby, with the Correspondance between ξ0 and Ξ0 , we obtain the following chained system resolution.

0.1 Ξ0 = 018kh, ξ0 = 21

By drawing up the 21 Base Table, we find :

(
|||| 0 = 0
{ 1 = 1
|| 8 = 8 .
||( k = 20
  h = 17
(7)

Or by performing a Base transposition since the 21 Base Table, we obtain :

(018kh)21 = (0.214 + 1.213 +8.212 + 20.21 + 17)10 = 13226
(8)

0.2 Ξ1 = 05a3c, ξ1 = 16

By drawing up the 16 Base Table, we find :

(
||0 = 0
||{5 = 5
 a = 10.
||||3 = 3
(c = 12
(9)

Or by performing a Base transposition since the 16 Base Table, we obtain :

(05a3c)16 = (5.163 + 10.162 + 3.16+ 12)10 = 23100
(10)

0.3 Ξ2 = 8064, ξ2 = 10

The specified base index ξ2 = 10, so any conversion is superfluous.

0.4 Ξ3 = 12vj, ξ3 = 34

By drawing up the 34 Base Table, we find :

(|1 = 1
|{2 = 2
|v = 31.
|(j = 19
(11)

Or by performing a Base transposition since the 34 Base Table, we obtain :

(12vj)34 = (1.343 + 2.342 + 31.34+ 19)10 = 42689
(12)

0.5 Ξ4 = 2gai, ξ4 = 28

By drawing up the 28 Base Table, we find :

(
||2 = 2
{g = 16
||a = 10.
(i = 18
(13)

Or by performing a Base transposition since the 28 Base Table, we obtain :

(2gai)  = (2.283 + 16.282 + 10.28+ 18) = 56746
      28                           10
(14)

0.6 Ξ5 = 0605a, ξ5 = 14

By drawing up the 14 Base Table, we find :

(|0 = 0
|{6 = 6
|5 = 5 .
|(a = 10
(15)

Or by performing a Base transposition since the 14 Base Table, we obtain :

               3
(0605a)14 = (6.14 + 5.14 + 10)10 = 16544
(16)

0.7 Ξ6 = 67500, ξ6 = 10

The specified base index ξ6 = 10, so any conversion is superfluous.

0.8 Ξ7 = 0ba30, ξ7 = 13

By drawing up the 13 Base Table, we find :

(|b = 11
|{a = 10
|3 = 3 .
|(0 = 0
(17)

Or by performing a Base transposition since the 13 Base Table, we obtain :

               3       2
(0ba30)13 = (11.13 + 10.13 + 3.13 + 13)10 = 25886
(18)

The Base transposition done, we could reverse the key to obtain the rest of the list.

Key build

We can use the following definition :

ρ is the length of the key ξ since Initialisation Section.

We go to compare the ρ length of ξ with χ the length of Ξ.We have χ=2.ρ

We will use the following terms :

To rebuild the missing half key, we go to reverse ξ with the following syntax

{
 ˚ξ = ξ⌢ ˜ξ                      if  χ  mod   2 = 0
 ˚ξ = ξ⌢ ˜ξ∕n                    if  χ   mod  2 = 1 .
(19)

Successive Base Transpositions - Step 2

Once the full key rebuilded from ξ, we could transpose again the rest of the list as step 1.

0.9 Ξ8 = 277a4, ξ8 = 13

By drawing up the 13 Base Table, we find :

(
||{2 = 2
 4 = 4 .
||(7 = 7
 a = 10
(20)

Or by performing a Base transposition since the 13 Base Table, we obtain :

(277a4)13 = (2.134+ 7.133 + 7.132 +10.13+ 4)10 = 73818
(21)

0.10 Ξ9 = 25376, ξ9 = 10

The specified base index ξ9 = 10, so any conversion is superfluous.

0.11 Ξ10 = 2a5db, ξ10 = 14

By drawing up the 14 Base Table, we find :

(
||||2 = 2
{5 = 5
||a = 10.
||(b = 11
 d = 13
(22)

Or by performing a Base transposition since the 14 Base Table, we obtain :

(2a5db)14 = (2.144+ 10.143 + 5.142 + 13.14 + 11)10 = 105445
(23)

0.12 Ξ11 = 5813, ξ11 = 28

By drawing up the 28 Base Table, we find :

(
||{ 1 = 1
  3 = 3 .
||( 5 = 5
  8 = 8
(24)

Or by performing a Base transposition since the 28 Base Table, we obtain :

(5813)28 = (5.283 + 8.282 + 1.28+ 3)10 = 116063
(25)

0.13 Ξ12 = 36u7, ξ12 = 34

By drawing up the 34 Base Table, we find :

(
||{ 3 = 3
  6 = 6 .
||( 7 = 7
  u = 30
(26)

Or by performing a Base transposition since the 34 Base Table, we obtain :

(36u7)34 = (3.343 + 6.342 + 30.34+ 7)10 = 125875
(27)

0.14 Ξ13 = 146367, ξ13 = 10

The specified base index ξ13 = 10, so any conversion is superfluous.

0.15 Ξ14 = 27706, ξ14 = 16

Or by performing a Base transposition since the 16 Base Table, we obtain :

                      3     2
(27706)16 = (2.164+ 7.16 + 7.16 + 6)10 = 161542
(28)

0.16 Ξ15 = 1j68c, ξ15 = 21

By drawing up the 21 Base Table, we find :

(
||||1 = 1
{6 = 6
||8 = 8 .
||(c = 12
 j = 19
(29)

Or by performing a Base transposition since the 21 Base Table, we obtain :

(1j68c)21 = (1.214+ 19.213 + 6.212 + 8.21+ 12)10 = 373266
(30)

We finnaly obtain the following numeric suit :

13226.23100.42689.56746.16544.67500.25886.73818.25376.105445.116063.125875.161542.373266

Chain Polynom Resolution

To continue the decrypting process, we know the suit increasing by recurrence. We can resolve the polynom using logic, we call it Ch.

Chn = y2+(y2+(y′′2+...+y(n)2)).y + c =0

The recursive injection of a polynome is resolvable uniquely using positive real roots.

With this definition, we will not keep cases with △≤ 0

In the last part of the demonstration, we will use the Chain Polynoms resolution algorithm defined by :

We gonna initialize the procedure with :

Conclusion

we can conclude using a simple ASCII table and get letters from the obtained numeric suit.

R={115,105,32,116,117,32,108,39,97,92,116,114,11,117,118,233}

ASCIIR={s,i, ,t,u, ,l,’,a, ,t,r,o,u,v,é }

We can get the final decrypted string : ”si tu l’a trouvé”