The ISAAC cipher: Difference between revisions

=={{header|FreeBASIC}}==

{{trans|C}}

<lang freebasic>' version 03-11-2016

' compile with: fbc -s console

Dim Shared As UInteger<32> randrsl(256), randcnt

Static Shared As UInteger<32> mm(256)

Static Shared As UInteger<32> aa, bb ,cc

Sub ISAAC()

Dim As UInteger<32> i, x, y

cc = cc + 1

bb = bb + cc

For i = 0 To 256 -1

x = mm(i)

Select Case (i Mod 4)

Case 0 : aa = aa Xor (aa Shl 13)

Case 1 : aa = aa Xor (aa Shr 6)

Case 2 : aa = aa Xor (aa Shl 2)

Case 3 : aa = aa Xor (aa Shr 16)

End Select

aa = mm((i+128) Mod 256) + aa

y = mm((x Shr 2) Mod 256) + aa + bb : mm(i) = y

bb = mm((y Shr 10) Mod 256) + x : randrsl(i) = bb

Next

randcnt = 0

End Sub

#Macro mix(a, b, c, d, e, f, g, h)

a Xor= b Shl 11 : d += a : b += c

b Xor= c Shr 2 : e += b : c += d

c Xor= d Shl 8 : f += c : d += e

d Xor= e Shr 16 : g += d : e += f

e Xor= f Shl 10 : h += e : f += g

f Xor= g Shr 4 : a += f : g += h

g Xor= h Shl 8 : b += g : h += a

h Xor= a Shr 9 : c += h : a += b

#EndMacro

Sub randinit(flag As Long)

Dim As Long i

Dim As UInteger<32> a = &H9e3779b9 '/* the golden ratio *

Dim As UInteger<32> b = &H9e3779b9

Dim As UInteger<32> c = &H9e3779b9

Dim As UInteger<32> d = &H9e3779b9

Dim As UInteger<32> e = &H9e3779b9

Dim As UInteger<32> f = &H9e3779b9

Dim As UInteger<32> g = &H9e3779b9

Dim As UInteger<32> h = &H9e3779b9

aa = 0 : bb = 0 : cc = 0

For i = 0 To 3

mix(a, b, c, d, e, f, g, h)

Next

For i = 0 To 255 Step 8

If flag = 1 Then

a += randrsl(i ) : b += randrsl(i +1)

c += randrsl(i +2) : d += randrsl(i +3)

e += randrsl(i +4) : f += randrsl(i +5)

g += randrsl(i +6) : h += randrsl(i +7)

mix(a, b, c, d, e, f, g, h)

mm(i ) = a : mm(i +1) = b : mm(i +2) = c : mm(i +3) = d

mm(i +4) = e : mm(i +5) = f : mm(i +6) = g : mm(i +7) = h

End If

Next

If flag = 1 Then

For i = 0 To 255 Step 8

a += mm(i ) : b += mm(i +1)

c += mm(i +2) : d += mm(i +3)

e += mm(i +4) : f += mm(i +5)

g += mm(i +6) : h += mm(i +7)

mix(a, b, c, d, e, f, g, h)

mm(i )= a : mm(i +1) = b : mm(i +2) = c : mm(i +3) = d

mm(i +4)= e : mm(i +5) = f : mm(i +6) = g : mm(i +7) = h

Next

End If

ISAAC()

randcnt = 0

End Sub

' // Get a random 32-bit value 0..MAXINT

Function iRandom() As UInteger<32>

Dim As UInteger<32> r = randrsl(randcnt)

randcnt += 1

If randcnt > 255 Then

ISAAC()

randcnt = 0

End If

Return r

End Function

' // Get a random character in printable ASCII range

Function iRandA() As UByte

Return iRandom() Mod 95 +32

End Function

' // Seed ISAAC with a string

Sub iSeed(seed As String, flag As Long)

Dim As ULong i, m = Len(seed) -1

For i = 0 To 255

mm(i) = 0

Next

For i = 0 To 255

If i > m Then

randrsl(i) = 0

Else

randrsl(i) = seed[i]

End If

Next

randinit(flag)

End Sub

' // maximum length of message

'#define MAXMSG 4096

#Define _MOD_ 95 ' mod is FreeBASIC keyword

#Define _START_ 32 ' start is used as variable name

' // cipher modes for Caesar

Enum ciphermode

mEncipher

mDecipher

mNone

End Enum

' // XOR cipher on random stream. Output: ASCII string

' no maximum lenght for input and output string

Function Vernam(msg As String) As String

Dim As ULong i

Dim As String v

For i = 0 To Len(msg) -1

v += Chr(iRandA() Xor msg[i])

Next

Return v

End Function

' // Caesar-shift a printable character

Function Ceasar(m As ciphermode, ch As UByte, shift As UByte, modulo As UByte, _

start As UByte) As UByte

' FreeBASIC Mod does not handle negative numbers correctly

' also there is litte problem with shift (declared UByte)

' the IIF() statement helps with shift

' to avoid a negative n a 8 times modulo is added

' modulo * 8 get translateted by FreeBASIC to modulo shl 3

Dim As Long n = (ch - start) + IIf(m = mDecipher, -shift, shift) + modulo * 8

n = n Mod modulo

Return start + n

End Function

' // Caesar-shift a string on a pseudo-random stream

Function CeasarStr(m As ciphermode, msg As String, modulo As UByte, _

start As UByte) As String

Dim As Long i

Dim As String v

For i = 0 To Len(msg) -1

v += Chr(Ceasar(m, msg[i], iRandA(), modulo, start))

Next

Return v

End Function

' ------=< MAIN >=------

Dim As Long n, l

Dim As String msg = "a Top Secret secret"

Dim As String key = "this is my secret key"

Dim As String vctx, vptx

Dim As String cctx, cptx

l = Len(msg)

' // Encrypt: Vernam XOR

iSeed(key, 1)

vctx = Vernam(msg)

' // Encrypt: Caesar

cctx = CeasarStr(mEncipher, msg, _mod_, _start_)

' // Decrypt: Vernam XOR

iSeed(key, 1)

vptx = Vernam(vctx)

' // Decrypt: Caesar

cptx = CeasarStr(mDecipher, cctx, _mod_, _start_)

Print "message: "; msg

Print " key: "; key

Print " XOR: ";

' // Output Vernam ciphertext as a string of hex digits

For n = 0 To l -1

Print Hex(vctx[n], 2);

Next

Print

' // Output Vernam decrypted plaintext

Print "XOR dcr: "; vptx

' // Caesar

Print " MOD: ";

' // Output Caesar ciphertext as a string of hex digits

For n= 0 To l -1

Print Hex(cctx[n], 2);

Next

Print

' // Output Caesar decrypted plaintext

Print "MOD dcr: " ; cptx

' empty keyboard buffer

While InKey <> "" : Wend

Print : Print "hit any key to end program"

Sleep

End</lang>

{{out}}

<pre>message: a Top Secret secret

key: this is my secret key

XOR: 1C0636190B1260233B35125F1E1D0E2F4C5422

XOR dcr: a Top Secret secret

MOD: 734270227D36772A783B4F2A5F206266236978

MOD dcr: a Top Secret secret</pre>