Public/Test-Encryption.ps1
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function Test-Encryption { <# .SYNOPSIS Test the signature created with the private key by using the public key. .DESCRIPTION Test the signature created with the private key by using the public key. .PARAMETER PublicKeyEncoded Specify the Base64 encoded string representation of the Public Key. .PARAMETER Signature Specify the Base64 encoded string representation of the signature coming from the inbound request. .PARAMETER Content Specify the content string that the signature coming from the inbound request is based upon. .NOTES Author: Nickolaj Andersen / Thomas Kurth Contact: @NickolajA Created: 2021-06-07 Updated: 2021-06-07 Version history: 1.0.0 - (2021-06-07) Function created Credits to Thomas Kurth for sharing his original C# code. #> param( [parameter(Mandatory = $true, HelpMessage = "Specify the Base64 encoded string representation of the Public Key.")] [ValidateNotNullOrEmpty()] [string]$PublicKeyEncoded, [parameter(Mandatory = $true, HelpMessage = "Specify the Base64 encoded string representation of the signature coming from the inbound request.")] [ValidateNotNullOrEmpty()] [string]$Signature, [parameter(Mandatory = $true, HelpMessage = "Specify the content string that the signature coming from the inbound request is based upon.")] [ValidateNotNullOrEmpty()] [string]$Content ) Process { # Convert from Base64 string to byte array $PublicKeyBytes = [System.Convert]::FromBase64String($PublicKeyEncoded) # Convert signature from Base64 string [byte[]]$Signature = [System.Convert]::FromBase64String($Signature) # Extract the modulus and exponent based on public key data $ExponentData = [System.Byte[]]::CreateInstance([System.Byte], 3) $ModulusData = [System.Byte[]]::CreateInstance([System.Byte], 256) [System.Array]::Copy($PublicKeyBytes, $PublicKeyBytes.Length - $ExponentData.Length, $ExponentData, 0, $ExponentData.Length) [System.Array]::Copy($PublicKeyBytes, 9, $ModulusData, 0, $ModulusData.Length) # Construct RSACryptoServiceProvider and import modolus and exponent data as parameters to reconstruct the public key from bytes $PublicKey = [System.Security.Cryptography.RSACryptoServiceProvider]::Create(2048) $RSAParameters = $PublicKey.ExportParameters($false) $RSAParameters.Modulus = $ModulusData $RSAParameters.Exponent = $ExponentData $PublicKey.ImportParameters($RSAParameters) # Construct a new SHA256Managed object to be used when computing the hash $SHA256Managed = New-Object -TypeName "System.Security.Cryptography.SHA256Managed" # Construct new UTF8 unicode encoding object $UnicodeEncoding = [System.Text.UnicodeEncoding]::UTF8 # Convert content to byte array [byte[]]$EncodedContentData = $UnicodeEncoding.GetBytes($Content) # Compute the hash [byte[]]$ComputedHash = $SHA256Managed.ComputeHash($EncodedContentData) # Verify the signature with the computed hash of the content using the public key $PublicKey.VerifyHash($ComputedHash, $Signature, [System.Security.Cryptography.HashAlgorithmName]::SHA256, [System.Security.Cryptography.RSASignaturePadding]::Pkcs1) } } |