PureBasic
PureBasic
ECDSA Sign and Verify
See more ECC Examples
Demonstrates how to create an ECDSA signature on the SHA256 hash of some data, and then verify.Chilkat PureBasic Downloads
IncludeFile "CkAsn.pb"
IncludeFile "CkBinData.pb"
IncludeFile "CkEcc.pb"
IncludeFile "CkPrivateKey.pb"
IncludeFile "CkPrng.pb"
IncludeFile "CkXml.pb"
IncludeFile "CkCrypt2.pb"
IncludeFile "CkPublicKey.pb"
Procedure ChilkatExample()
success.i = 0
; 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.
privKey.i = CkPrivateKey::ckCreate()
If privKey.i = 0
Debug "Failed to create object."
ProcedureReturn
EndIf
success = CkPrivateKey::ckLoadEncryptedPemFile(privKey,"qa_data/ecc/secp256r1-key-pkcs8-secret.pem","secret")
If success = 0
Debug CkPrivateKey::ckLastErrorText(privKey)
CkPrivateKey::ckDispose(privKey)
ProcedureReturn
EndIf
; Sign the SHA256 hash of some data.
bd.i = CkBinData::ckCreate()
If bd.i = 0
Debug "Failed to create object."
ProcedureReturn
EndIf
success = CkBinData::ckLoadFile(bd,"qa_data/hamlet.xml")
If success = 0
Debug "Failed to load file to be hashed."
CkPrivateKey::ckDispose(privKey)
CkBinData::ckDispose(bd)
ProcedureReturn
EndIf
crypt.i = CkCrypt2::ckCreate()
If crypt.i = 0
Debug "Failed to create object."
ProcedureReturn
EndIf
CkCrypt2::setCkHashAlgorithm(crypt, "sha256")
CkCrypt2::setCkEncodingMode(crypt, "base64")
hashStr.s = CkCrypt2::ckHashBdENC(crypt,bd)
ecdsa.i = CkEcc::ckCreate()
If ecdsa.i = 0
Debug "Failed to create object."
ProcedureReturn
EndIf
prng.i = CkPrng::ckCreate()
If prng.i = 0
Debug "Failed to create object."
ProcedureReturn
EndIf
; Returns ASN.1 signature as a base64 string.
sig.s = CkEcc::ckSignHashENC(ecdsa,hashStr,"base64",privKey,prng)
Debug "sig = " + 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:
asn.i = CkAsn::ckCreate()
If asn.i = 0
Debug "Failed to create object."
ProcedureReturn
EndIf
CkAsn::ckLoadEncoded(asn,sig,"base64")
xml.i = CkXml::ckCreate()
If xml.i = 0
Debug "Failed to create object."
ProcedureReturn
EndIf
CkXml::ckLoadXml(xml,CkAsn::ckAsnToXml(asn))
Debug CkXml::ckGetXml(xml)
; 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.s = CkXml::ckGetChildContentByIndex(xml,0)
s.s = CkXml::ckGetChildContentByIndex(xml,1)
Debug "r = " + r
Debug "s = " + s
; --------------------------------------------------------------------
; Now verify against the hash of the original data.
; Get the corresponding public key.
pubKey.i = CkPublicKey::ckCreate()
If pubKey.i = 0
Debug "Failed to create object."
ProcedureReturn
EndIf
success = CkPublicKey::ckLoadFromFile(pubKey,"qa_data/ecc/secp256r1-pub.pem")
If success = 0
Debug CkPublicKey::ckLastErrorText(pubKey)
CkPrivateKey::ckDispose(privKey)
CkBinData::ckDispose(bd)
CkCrypt2::ckDispose(crypt)
CkEcc::ckDispose(ecdsa)
CkPrng::ckDispose(prng)
CkAsn::ckDispose(asn)
CkXml::ckDispose(xml)
CkPublicKey::ckDispose(pubKey)
ProcedureReturn
EndIf
; We already have the SHA256 hash of the original data (hashStr) so no need to re-do it..
ecc2.i = CkEcc::ckCreate()
If ecc2.i = 0
Debug "Failed to create object."
ProcedureReturn
EndIf
result.i = CkEcc::ckVerifyHashENC(ecc2,hashStr,sig,"base64",pubKey)
If result <> 1
Debug CkEcc::ckLastErrorText(ecc2)
CkPrivateKey::ckDispose(privKey)
CkBinData::ckDispose(bd)
CkCrypt2::ckDispose(crypt)
CkEcc::ckDispose(ecdsa)
CkPrng::ckDispose(prng)
CkAsn::ckDispose(asn)
CkXml::ckDispose(xml)
CkPublicKey::ckDispose(pubKey)
CkEcc::ckDispose(ecc2)
ProcedureReturn
EndIf
Debug "Verified!"
; Note: If we have only r,s and wish to reconstruct the ASN.1 signature, we do it like this:
xml2.i = CkXml::ckCreate()
If xml2.i = 0
Debug "Failed to create object."
ProcedureReturn
EndIf
CkXml::setCkTag(xml2, "sequence")
CkXml::ckNewChild2(xml2,"int",r)
CkXml::ckNewChild2(xml2,"int",s)
asn2.i = CkAsn::ckCreate()
If asn2.i = 0
Debug "Failed to create object."
ProcedureReturn
EndIf
CkAsn::ckLoadAsnXml(asn2,CkXml::ckGetXml(xml2))
encodedSig.s = CkAsn::ckGetEncodedDer(asn2,"base64")
Debug "encoded DSS signature: " + 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...
CkPrivateKey::ckDispose(privKey)
CkBinData::ckDispose(bd)
CkCrypt2::ckDispose(crypt)
CkEcc::ckDispose(ecdsa)
CkPrng::ckDispose(prng)
CkAsn::ckDispose(asn)
CkXml::ckDispose(xml)
CkPublicKey::ckDispose(pubKey)
CkEcc::ckDispose(ecc2)
CkXml::ckDispose(xml2)
CkAsn::ckDispose(asn2)
ProcedureReturn
EndProcedure