RSA crypto with Windows CSP
Posted: Mon May 15, 2017 9:30 pm
CSP is the only out-of-the-box solution for RSA on Windows. I've searched and seen a lot of threads on CSP here but the few using RSA were basically quick demos of encrypting and decryption using CSP storage and little configuration and none of them actually exported keys.
From what I've read on MSDN my code actually generates the key pairs and exports them, but I've yet to get the encryption to use these external keys. Has anyone had any luck saving keys outside of the CSP container and using them later?
I wrote this in a couple days worth of spare time using MSDN. It should be working I just haven't seen any CSP based demos of exporting keys. According to MSDN this should be working. You should be able to Base64 rsa\pub and share it and decrypt with rsa\priv.
From what I've read on MSDN my code actually generates the key pairs and exports them, but I've yet to get the encryption to use these external keys. Has anyone had any luck saving keys outside of the CSP container and using them later?
I wrote this in a couple days worth of spare time using MSDN. It should be working I just haven't seen any CSP based demos of exporting keys. According to MSDN this should be working. You should be able to Base64 rsa\pub and share it and decrypt with rsa\priv.
Code: Select all
#PROV_RSA_FULL = 1
#CRYPT_NEWKEYSET = 8
#CRYPT_DELETEKEYSET = 16
#CRYPT_EXPORTABLE = 1
#CALG_RSA_KEYX = 41984
#MS_DEF_PROV = "Microsoft Base Cryptographic Provider v1.0"
#MS_STRONG_PROV = "Microsoft Strong Cryptographic Provider"
#MS_ENHANCED_PROV = "Microsoft Enhanced Cryptographic Provider v1.0"
#CRYPT_VERIFYCONTEXT = -268435456
#PUBLICKEYBLOB = $06;
#PRIVATEKEYBLOB = $07;
#PLANTEXTKEYBLOB = $08;
#OPAQUEKEYBLOB = $09 ;
#CRYPT_EXPORTABLE = 1
Structure mykeys
*priv
*pub
keysize.l
EndStructure
Global rsa.mykeys
rsa\priv=AllocateMemory(4096)
rsa\pub=AllocateMemory(4096)
Procedure encrypt(*mem,length,*key)
If CryptAcquireContext_(@hProv, #Null, #MS_STRONG_PROV, #PROV_RSA_FULL, #CRYPT_VERIFYCONTEXT) = 0
CryptAcquireContext_(@hProv, #Null, #MS_STRONG_PROV, #PROV_RSA_FULL, #CRYPT_NEWKEYSET|#CRYPT_VERIFYCONTEXT)
EndIf
If CryptImportKey_(hProv,*key,rsa\keysize,0,0,@hKey)
CryptEncrypt_(hKey,0,1,$40,*mem,@length,rsa\keysize)
CryptDestroyKey_(hKey)
EndIf
If hProv : CryptReleaseContext_(hProv,0) : EndIf
EndProcedure
Procedure decrypt(*mem,length,*key)
If CryptAcquireContext_(@hProv, #Null, #MS_STRONG_PROV, #PROV_RSA_FULL, #CRYPT_VERIFYCONTEXT) = 0
CryptAcquireContext_(@hProv, #Null, #MS_STRONG_PROV, #PROV_RSA_FULL, #CRYPT_NEWKEYSET|#CRYPT_VERIFYCONTEXT)
EndIf
If CryptImportKey_(hProv,*key,rsa\keysize,0,0,@hKey)
CryptDecrypt_(hKey,0,1,$40,*mem,rsa\keysize)
CryptDestroyKey_(hKey)
EndIf
If hProv : CryptReleaseContext_(hProv,0) : EndIf
EndProcedure
Procedure makekeys(*private,*public)
If CryptAcquireContext_(@hProv, #Null, #MS_STRONG_PROV, #PROV_RSA_FULL, #CRYPT_VERIFYCONTEXT) = 0
CryptAcquireContext_(@hProv, #Null, #MS_STRONG_PROV, #PROV_RSA_FULL, #CRYPT_NEWKEYSET|#CRYPT_VERIFYCONTEXT)
EndIf
;make RSA keypair
CryptGenKey_(hProv,#CALG_RSA_KEYX,#CRYPT_EXPORTABLE,@hKey)
;set public key
CryptExportKey_(hKey,0,#PUBLICKEYBLOB,0,0,@keylength)
*publickey=AllocateMemory(keylength)
CryptExportKey_(hKey,0,#PUBLICKEYBLOB,0,*publickey,@keylength)
;set private key
CryptExportKey_(hKey,0,#PRIVATEKEYBLOB,0,0,@keylength)
*privatekey=AllocateMemory(keylength)
CryptExportKey_(hKey,0,#PRIVATEKEYBLOB,0,*privatekey,@keylength)
CryptDestroyKey_(hKey)
CryptReleaseContext_(hProv,0)
;according to MSDN this is what actually deletes key pair from CSP
If CryptAcquireContext_(@hProv,#Null,#MS_STRONG_PROV,#PROV_RSA_FULL,#CRYPT_DELETEKEYSET)
CryptReleaseContext_(hProv,0)
EndIf
rsa\keysize=keylength
CopyMemory(*privatekey,*private,MemorySize(*privatekey))
CopyMemory(*publicKey,*public,MemorySize(*publicKey))
FreeMemory(*privatekey)
FreeMemory(*publickey)
EndProcedure
string.s="Hallo12345678"
*cipherBlock=AllocateMemory(StringByteLength(string)-1)
PokeS(*cipherBlock,string,Len(string),#PB_String_NoZero)
makekeys(rsa\priv,rsa\pub)
encrypt(*cipherBlock,MemorySize(*cipherBlock),rsa\pub)
Debug PeekS(*cipherBlock,MemorySize(*cipherBlock),#PB_Unicode)
Debug PeekS(*cipherBlock,MemorySize(*cipherBlock),#PB_Ascii)
Debug PeekS(*cipherBlock,MemorySize(*cipherBlock),#PB_UTF8)
decrypt(*cipherBlock,MemorySize(*cipherBlock),rsa\priv)
Debug PeekS(*cipherBlock,MemorySize(*cipherBlock),#PB_Unicode)
Debug PeekS(*cipherBlock,MemorySize(*cipherBlock),#PB_Ascii)
Debug PeekS(*cipherBlock,MemorySize(*cipherBlock),#PB_UTF8)
End
