CryptoSys API Library Manual

CIPHER_Update

Encrypts or decrypts a chunk of input (in incremental mode).

VBA/VB6 Syntax

Public Declare Function CIPHER_Update Lib "diCryptoSys.dll" (ByVal hContext As Long, ByRef lpOutput As Byte, ByVal nOutBytes As Long, ByRef lpData As Byte, ByVal nDataLen As Long) As Long

nRet = CIPHER_Update(hContext, lpOutput(0), nOutBytes, lpData(0), nDataLen)

C/C++ Syntax

long __stdcall CIPHER_Update(long hContext, unsigned char *lpOutput, long nOutBytes, const unsigned char *lpData, long nDataLen);

Parameters

hContext
[in] Handle to the CIPHER context.
lpOutput
[out] Byte array to receive output.
nOutBytes
[in] Length of output array in bytes.
lpData
[in] Input data to be processed.
nDataLen
[in] Length of input data in bytes.

Returns (VBA/C)

If successful, the return value is 0; otherwise it returns a non-zero error code.

VBA Wrapper Syntax

Public Function cipherUpdate(hContext As Long, lpData() As Byte) As Byte()

.NET Equivalent

Cipher.Update Method (Byte[])

C++ (STL) Equivalent

crsysapi::bvec_t crsysapi::Cipher::Update (const bvec_t &data)

Remarks

The handle hContext to the CIPHER context must have been set up with a prior call to CIPHER_Init or CIPHER_InitHex.

The chunks of data to be en/decrypted must be passed to the Update function in sequential order and only in lengths which are multiples of the block size (16 bytes for AES, 8 for Triple DES). For ECB and CBC modes, the last block in the sequence must be suitably padded to a length a multiple of the block size. For other modes, e.g. CTR, the last block in the sequence may be shorter than a multiple of the block length. However, once this final, shorter block has been processed, the Update function can no longer be used (well it can, but the output is wrong).

Example (VBA core function)

' Using the "raw" functions
Dim key() As Byte
Dim iv() As Byte
Dim pt() As Byte
Dim ct() As Byte
Dim ok() As Byte
Dim ptlen As Long
Dim ctlen As Long
Dim keylen As Long
Dim ivlen As Long
Dim algstr As String
Dim hContext As Long
Dim nRet As Long

key = cnvBytesFromHexStr("0123456789ABCDEFF0E1D2C3B4A59687")
iv = cnvBytesFromHexStr("FEDCBA9876543210FEDCBA9876543210")
keylen = cnvBytesLen(key)
ivlen = cnvBytesLen(iv)
Debug.Print "KY=" & cnvHexStrFromBytes(key)
Debug.Print "IV=" & cnvHexStrFromBytes(iv)

' TEST 1 - CBC mode
algstr = "Aes128/CBC"
Debug.Print algstr
' Initialize context for repeated chunks
hContext = CIPHER_Init(ENCRYPT, algstr, key(0), keylen, iv(0), ivlen, 0)
Debug.Print "CIPHER_Init returns 0x" & Hex(hContext) & " (expected NON-zero)"
Debug.Assert hContext <> 0

' Pass data in chunks of 16 bytes (or multiples of)
' Part 1...
pt = StrConv("Now is the time for all good men", vbFromUnicode)
Debug.Print "PT=" & cnvHexStrFromBytes(pt)
ptlen = cnvBytesLen(pt)
ctlen = ptlen
ReDim ct(ctlen - 1)
nRet = CIPHER_Update(hContext, ct(0), ctlen, pt(0), ptlen)
Debug.Print "CIPHER_Update returns " & nRet & " (expected 0)"
Debug.Print "CT=" & cnvHexStrFromBytes(ct)

' Part 2...
pt = StrConv(" to come to the aid of the party", vbFromUnicode)
Debug.Print "PT=" & cnvHexStrFromBytes(pt)
ptlen = cnvBytesLen(pt)
ctlen = ptlen
ReDim ct(ctlen - 1)
nRet = CIPHER_Update(hContext, ct(0), ctlen, pt(0), ptlen)
Debug.Print "CIPHER_Update returns " & nRet & " (expected 0)"
Debug.Print "CT=" & cnvHexStrFromBytes(ct)

' We are done
nRet = CIPHER_Final(hContext)
Debug.Print "CIPHER_Final returns " & nRet & " (expected 0)"

Example (VBA wrapper function)

' Using the wrapper functions
Dim key() As Byte
Dim iv() As Byte
Dim pt() As Byte
Dim ct() As Byte
Dim algstr As String
Dim hContext As Long
Dim nRet As Long

key = cnvBytesFromHexStr("0123456789ABCDEFF0E1D2C3B4A59687")
iv = cnvBytesFromHexStr("FEDCBA9876543210FEDCBA9876543210")
Debug.Print "KY=" & cnvHexStrFromBytes(key)
Debug.Print "IV=" & cnvHexStrFromBytes(iv)

' TEST 1 - CBC mode
algstr = "Aes128/CBC"
Debug.Print algstr
' Initialize context for repeated chunks
hContext = cipherInit(ENCRYPT, algstr, key, iv)
Debug.Print "cipherInit returns 0x" & Hex(hContext) & " (expected NON-zero)"
Debug.Assert hContext <> 0

' Pass data in chunks of 16 bytes (or multiples of)
' Part 1...
pt = StrConv("Now is the time for all good men", vbFromUnicode)
Debug.Print "PT=" & cnvHexStrFromBytes(pt)
ct = cipherUpdate(hContext, pt)
Debug.Print "CT=" & cnvHexStrFromBytes(ct)

' Part 2...
pt = StrConv(" to come to the aid of the party", vbFromUnicode)
Debug.Print "PT=" & cnvHexStrFromBytes(pt)
ct = cipherUpdate(hContext, pt)
Debug.Print "CT=" & cnvHexStrFromBytes(ct)

' We are done
nRet = cipherFinal(hContext)
Debug.Print "cipherFinal returns " & nRet & " (expected 0)"

' TEST 2 - ECB mode
algstr = "Aes128/ecb"
Debug.Print algstr
Dim dummy() As Byte
' Initialize context for repeated chunks
hContext = cipherInit(ENCRYPT, algstr, key, dummy)
Debug.Print "cipherInit returns 0x" & Hex(hContext) & " (expected NON-zero)"
Debug.Assert hContext <> 0

' Pass data in chunks of 16 bytes (or multiples of)
' Part 1...
pt = StrConv("Now is the time for all good men", vbFromUnicode)
Debug.Print "PT=" & cnvHexStrFromBytes(pt)
ct = cipherUpdate(hContext, pt)
Debug.Print "CT=" & cnvHexStrFromBytes(ct)

' Part 2...
pt = StrConv(" to come to the aid of the party", vbFromUnicode)
Debug.Print "PT=" & cnvHexStrFromBytes(pt)
ct = cipherUpdate(hContext, pt)
Debug.Print "CT=" & cnvHexStrFromBytes(ct)

' We are done
nRet = cipherFinal(hContext)
Debug.Assert nRet = 0

' TEST 3 - CTR mode
algstr = "Aes128/ctr"
Debug.Print algstr
' Initialize context for repeated chunks
hContext = cipherInit(ENCRYPT, algstr, key, iv)
Debug.Print "cipherInit returns 0x" & Hex(hContext) & " (expected NON-zero)"
Debug.Assert hContext <> 0

' Pass data in chunks of 16 bytes (or multiples of)
' Part 1...
pt = StrConv("Now is the time for all good men", vbFromUnicode)
Debug.Print "PT=" & cnvHexStrFromBytes(pt)
ct = cipherUpdate(hContext, pt)
Debug.Print "CT=" & cnvHexStrFromBytes(ct)

' Part 2...
' In CTR mode (and OFB and CFB) the last block need not be a multiple
pt = StrConv(" to come to the aid of", vbFromUnicode)
Debug.Print "PT=" & cnvHexStrFromBytes(pt)
ct = cipherUpdate(hContext, pt)
Debug.Print "CT=" & cnvHexStrFromBytes(ct)

' We are done
nRet = cipherFinal(hContext)
Debug.Assert nRet = 0

KY=0123456789ABCDEFF0E1D2C3B4A59687
IV=FEDCBA9876543210FEDCBA9876543210
Aes128/CBC
cipherInit returns 0x2AB4B01D (expected NON-zero)
PT=4E6F77206973207468652074696D6520666F7220616C6C20676F6F64206D656E
CT=C3153108A8DD340C0BCB1DFE8D25D2320EE0E66BD2BB4A313FB75C5638E9E177
PT=20746F20636F6D6520746F2074686520616964206F6620746865207061727479
CT=211FC26A1FF51CE35741B76A77DB6DE21EE94708B546919999A4557F43AAA2BB
cipherFinal returns 0 (expected 0)
Aes128/ecb
cipherInit returns 0x243820F9 (expected NON-zero)
PT=4E6F77206973207468652074696D6520666F7220616C6C20676F6F64206D656E
CT=F0D1AD6F901FFFAE5572A6928DAB52B064B25C79F876730321E36DC01011ACCE
PT=20746F20636F6D6520746F2074686520616964206F6620746865207061727479
CT=02D6F240643271217758C44862BB1B6862CD10757387256BC678A1708483862A
Aes128/ctr
cipherInit returns 0x5FFB439 (expected NON-zero)
PT=4E6F77206973207468652074696D6520666F7220616C6C20676F6F64206D656E
CT=3FAC68CBAE6D774151306E9DB16CE0191C51E91959DA4F082B7CE3498C2D20D7
PT=20746F20636F6D6520746F2074686520616964206F66
CT=8437EC92088FE4C19FB49BDF2BADF7C7FD6FB9A7D52A

See Also

CIPHER_Init CIPHER_Final

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