GeraDigitosAleatorios.bas

Attribute VB_Name = "GeraDigitosAleatorios"
Option Explicit

Private Declare Function BCryptGenRandom Lib "bcrypt.dll" (ByVal hAlgorithm As Long, ByRef pbBuffer As Long, ByVal cbBuffer As Long, ByVal dwFlags As Long) As Long
Const BCRYPT_USE_SYSTEM_PREFERRED_RNG = &H2
Const STATUS_SUCCESS = &H0

Public Function GeraDigitosAleatorios(ByVal tamanho As Integer) As String

    Const ERRO_GERACAO_SEQUENCIA_NUMERO = vbObjectError + 1
    Const ERRO_GERACAO_SEQUENCIA_DESCRICAO = "Erro na geração da sequência aleatória"
    
    Dim numero As Long
    GeraDigitosAleatorios = ""
    While Len(GeraDigitosAleatorios) < tamanho
        If STATUS_SUCCESS <> BCryptGenRandom(0, numero, 4&, BCRYPT_USE_SYSTEM_PREFERRED_RNG) Then
            Err.Raise Number:=ERRO_GERACAO_SEQUENCIA_NUMERO, _
                      Description:=ERRO_GERACAO_SEQUENCIA_DESCRICAO
        End If
            
        GeraDigitosAleatorios = GeraDigitosAleatorios + CStr(Abs(numero))
    Wend

    GeraDigitosAleatorios = Right(GeraDigitosAleatorios, tamanho)
End Function

'##################################
'  Exemplo de Utilização
'##################################
'Private Sub Command1_Click()
'    MsgBox GeraDigitosAleatorios(8)
'End Sub