(PowerBuilder) ECDSA Sign and Verify

Demonstrates how to create an ECDSA signature on the SHA256 hash of some data, and then verify.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

integer li_rc
oleobject loo_PrivKey
integer li_Success
oleobject loo_Bd
oleobject loo_Crypt
string ls_HashStr
oleobject loo_Ecdsa
oleobject loo_Prng
string ls_Sig
oleobject loo_Asn
oleobject loo_Xml
string r
string s
oleobject loo_PubKey
oleobject loo_Ecc2
integer li_Result
oleobject loo_Xml2
oleobject loo_Asn2
string ls_EncodedSig

// This example assumes the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

// First load an ECDSA private key to be used for signing.
loo_PrivKey = create oleobject
// Use "Chilkat_9_5_0.PrivateKey" for versions of Chilkat < 10.0.0
li_rc = loo_PrivKey.ConnectToNewObject("Chilkat.PrivateKey")
if li_rc < 0 then
    destroy loo_PrivKey
    MessageBox("Error","Connecting to COM object failed")
    return
end if
li_Success = loo_PrivKey.LoadEncryptedPemFile("qa_data/ecc/secp256r1-key-pkcs8-secret.pem","secret")
if li_Success = 0 then
    Write-Debug loo_PrivKey.LastErrorText
    destroy loo_PrivKey
    return
end if

// Sign the SHA256 hash of some data.
loo_Bd = create oleobject
// Use "Chilkat_9_5_0.BinData" for versions of Chilkat < 10.0.0
li_rc = loo_Bd.ConnectToNewObject("Chilkat.BinData")

li_Success = loo_Bd.LoadFile("qa_data/hamlet.xml")
if li_Success = 0 then
    Write-Debug "Failed to load file to be hashed."
    destroy loo_PrivKey
    destroy loo_Bd
    return
end if

loo_Crypt = create oleobject
// Use "Chilkat_9_5_0.Crypt2" for versions of Chilkat < 10.0.0
li_rc = loo_Crypt.ConnectToNewObject("Chilkat.Crypt2")

loo_Crypt.HashAlgorithm = "sha256"
loo_Crypt.EncodingMode = "base64"
ls_HashStr = loo_Crypt.HashBdENC(loo_Bd)

loo_Ecdsa = create oleobject
// Use "Chilkat_9_5_0.Ecc" for versions of Chilkat < 10.0.0
li_rc = loo_Ecdsa.ConnectToNewObject("Chilkat.Ecc")

loo_Prng = create oleobject
// Use "Chilkat_9_5_0.Prng" for versions of Chilkat < 10.0.0
li_rc = loo_Prng.ConnectToNewObject("Chilkat.Prng")

// Returns ASN.1 signature as a base64 string.
ls_Sig = loo_Ecdsa.SignHashENC(ls_HashStr,"base64",loo_PrivKey,loo_Prng)
Write-Debug "sig = " + ls_Sig

// The signature is in ASN.1 format (which may be described as the "encoded DSS signature").
// SEQUENCE (2 elem)
//   INTEGER (255 bit) 4849395540832462044300553275435608522154141569743642905628579547100940...
//   INTEGER (255 bit) 3680701124244788134409868118208591399799457104230118295614152238560005...

// If you wish, you can get the r and s components of the signature like this:
loo_Asn = create oleobject
// Use "Chilkat_9_5_0.Asn" for versions of Chilkat < 10.0.0
li_rc = loo_Asn.ConnectToNewObject("Chilkat.Asn")

loo_Asn.LoadEncoded(ls_Sig,"base64")
loo_Xml = create oleobject
// Use "Chilkat_9_5_0.Xml" for versions of Chilkat < 10.0.0
li_rc = loo_Xml.ConnectToNewObject("Chilkat.Xml")

loo_Xml.LoadXml(loo_Asn.AsnToXml())

Write-Debug loo_Xml.GetXml()

// We now have this:
// <?xml version="1.0" encoding="utf-8"?>
// <sequence>
//     <int>6650D422D86BA4A228B5617604E59052591B9B2C32EF324C44D09EF67E5F0060</int>
//     <int>0CFD9F6AC85042FC70F672C141BA6B2A4CAFBB906C3D907BCCC1BED62B28326F</int>
// </sequence>

// Get the "r" and "s" as hex strings
r = loo_Xml.GetChildContentByIndex(0)
s = loo_Xml.GetChildContentByIndex(1)

Write-Debug "r = " + r
Write-Debug "s = " + s

// --------------------------------------------------------------------
// Now verify against the hash of the original data.

// Get the corresponding public key.
loo_PubKey = create oleobject
// Use "Chilkat_9_5_0.PublicKey" for versions of Chilkat < 10.0.0
li_rc = loo_PubKey.ConnectToNewObject("Chilkat.PublicKey")

li_Success = loo_PubKey.LoadFromFile("qa_data/ecc/secp256r1-pub.pem")
if li_Success = 0 then
    Write-Debug loo_PubKey.LastErrorText
    destroy loo_PrivKey
    destroy loo_Bd
    destroy loo_Crypt
    destroy loo_Ecdsa
    destroy loo_Prng
    destroy loo_Asn
    destroy loo_Xml
    destroy loo_PubKey
    return
end if

// We already have the SHA256 hash of the original data (hashStr) so no need to re-do it..
loo_Ecc2 = create oleobject
// Use "Chilkat_9_5_0.Ecc" for versions of Chilkat < 10.0.0
li_rc = loo_Ecc2.ConnectToNewObject("Chilkat.Ecc")

li_Result = loo_Ecc2.VerifyHashENC(ls_HashStr,ls_Sig,"base64",loo_PubKey)
if li_Result <> 1 then
    Write-Debug loo_Ecc2.LastErrorText
    destroy loo_PrivKey
    destroy loo_Bd
    destroy loo_Crypt
    destroy loo_Ecdsa
    destroy loo_Prng
    destroy loo_Asn
    destroy loo_Xml
    destroy loo_PubKey
    destroy loo_Ecc2
    return
end if

Write-Debug "Verified!"

// Note: If we have only r,s and wish to reconstruct the ASN.1 signature, we do it like this:
loo_Xml2 = create oleobject
// Use "Chilkat_9_5_0.Xml" for versions of Chilkat < 10.0.0
li_rc = loo_Xml2.ConnectToNewObject("Chilkat.Xml")

loo_Xml2.Tag = "sequence"
loo_Xml2.NewChild2("int",r)
loo_Xml2.NewChild2("int",s)

loo_Asn2 = create oleobject
// Use "Chilkat_9_5_0.Asn" for versions of Chilkat < 10.0.0
li_rc = loo_Asn2.ConnectToNewObject("Chilkat.Asn")

loo_Asn2.LoadAsnXml(loo_Xml2.GetXml())
ls_EncodedSig = loo_Asn2.GetEncodedDer("base64")
Write-Debug "encoded DSS signature: " + ls_EncodedSig

// You can go to https://lapo.it/asn1js/  and copy/paste the base64 encodedSig into the online tool, then press the "decode" button.
// You will see the ASN.1 such as this:

// SEQUENCE (2 elem)
//   INTEGER (255 bit) 4849395540832462044300553275435608522154141569743642905628579547100940...
//   INTEGER (255 bit) 3680701124244788134409868118208591399799457104230118295614152238560005...


destroy loo_PrivKey
destroy loo_Bd
destroy loo_Crypt
destroy loo_Ecdsa
destroy loo_Prng
destroy loo_Asn
destroy loo_Xml
destroy loo_PubKey
destroy loo_Ecc2
destroy loo_Xml2
destroy loo_Asn2