encrypt/decrypt strings using AES
Posted: Mon Aug 19, 2013 4:51 am
I assume this has been approached many times, here is my version (combines the power of AES with Base64)!
Code: Select all
; Encrypt/Decrypt any string using AES256-CBC + Base64
; Base64 is used to hide zero-bytes '\0' that could be generated by AES
; Ascii/Unicode
; Said - Aug 2013
EnableExplicit
; some random generated data uisng CryptRandom()
; size of Key = 32 (AES-256Bits)
; size of InitVect = 16 (CBC)
; PaddingB64 is a random 64-char string needed for padding short strings used with Base64Encoding and AES
DataSection
ENC_Key:
Data.b $5B,$2C,$CE,$6E,$4E,$D9,$9D,$0B,$08,$AE,$24,$2C,$D6,$49,$CF,$BB,$A8,$CE,$DC,$9C,$C9,$09,$CF,$E6,$88,$CC,$07,$14,$11,$AA,$6B,$60
ENC_InitVect:
Data.b $8C,$0D,$4E,$ED,$67,$96,$FB,$F0,$D3,$72,$87,$35,$3E,$BE,$42,$A2
ENC_PaddingB64:
Data.s "c1e39477b19d95223577a457960959be693060b0c683ec7aaf127d87807c6e02"
EndDataSection
Procedure.i _EncBuffer(*Input, *Output)
If (MemorySize(*Input) >= 16) And (MemorySize(*Input) = MemorySize(*Output))
If AESEncoder(*Input, *Output, MemorySize(*Input), ?ENC_Key, 256, ?ENC_InitVect, #PB_Cipher_CBC)
ProcedureReturn #True
EndIf
EndIf
ProcedureReturn #False ; AES cant encrypt a memory block with size < 16
EndProcedure
Procedure.i _DecBuffer(*Input, *Output)
If (MemorySize(*Input) >= 16) And (MemorySize(*Input) = MemorySize(*Output))
If AESDecoder(*Input, *Output, MemorySize(*Input), ?ENC_Key, 256, ?ENC_InitVect, #PB_Cipher_CBC)
ProcedureReturn #True
EndIf
EndIf
ProcedureReturn #False ; AES cant encrypt a memory block with size < 16
EndProcedure
Procedure.s EncString(in.s)
Protected paddStr.s, wrd.s, out.s, *p, *mb0, *mb1, *mb2, n0, n1, n2
If in = "" : ProcedureReturn "" : EndIf
Restore ENC_PaddingB64
Read.s paddStr
; we always padd as input could be too short
n0 = StringByteLength(paddStr) + StringByteLength(in) + SizeOf(Character)
*mb0 = AllocateMemory(n0) : *p = *mb0
CopyMemoryString(@paddStr, @*p)
CopyMemoryString(@in)
; encrypting using AES
n1 = n0
*mb1 = AllocateMemory(n1)
_EncBuffer(*mb0, *mb1)
; encoding encrypted buffer using Base64 to mask \0 if any (needed for PeekS())
n2 = n1 * 1.4
*mb2 = AllocateMemory(n2)
Base64Encoder(*mb1, n1, *mb2, n2)
; encrypted buffer is now ready for PeekS()
out = PeekS(*mb2)
FreeMemory(*mb0)
FreeMemory(*mb1)
FreeMemory(*mb2)
ProcedureReturn out
EndProcedure
Procedure.s DecString(in.s)
; decrypts a string encrypted with EncString()
Protected paddStr.s, wrd.s, out.s, *mb1, *mb2, n0, n1, n2
If in = "" : ProcedureReturn "" : EndIf
; decode encrypted string using Base64 --> encrypted-buffer
n0 = StringByteLength(in)
*mb1 = AllocateMemory(n0)
n1 = Base64Decoder(@in, n0, *mb1, n0)
*mb1 = ReAllocateMemory(*mb1, n1) ; adjust size fo encrypted-buffer!
n2 = n1
*mb2 = AllocateMemory(n2)
_DecBuffer(*mb1, *mb2)
wrd = PeekS(*mb2)
Restore ENC_PaddingB64
Read.s paddStr
If Mid(wrd, 1, Len(paddStr)) = paddStr
out = Mid(wrd, Len(paddStr)+1)
EndIf
FreeMemory(*mb1)
FreeMemory(*mb2)
ProcedureReturn out
EndProcedure
; test
CompilerIf #PB_Compiler_IsMainFile
Global i, n, *mb, org.s, enc.s, dec.s
; test short string
org = "string"
enc = EncString(org)
dec = DecString(enc)
; random tests
n = 10000
*mb = AllocateMemory(n+2)
For i = 1 To 1000
RandomData(*mb, n)
org = PeekS(*mb)
enc = EncString(org)
dec = DecString(enc)
If dec = org
;Debug "ok L = " + Str(Len(org))
Else
Debug ">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> failed L = " + Str(Len(org))
EndIf
Next
FreeMemory(*mb)
CompilerEndIf
... it is still much easier to handle with readily available routines in PB, so no wonder you will mostly find in the forums routines that make use of Base64 PB functions when dealing with encrypting/decrypting.