(AutoIt) Understanding a few ECDSA Public Key Formats

See more ECC Examples

Describes a few ECDSA public key formats.

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

; Here we have the output of the following openssl command:  openssl ec -in key.pem -pubout -text

; Private-Key: (256 bit)
; priv:
;     0e:63:25:8a:73:3c:71:b6:c0:e7:a3:0f:94:b9:74:
;     e0:be:bd:46:18:be:40:7e:66:9e:21:99:85:0e:ed:
;     87:2d
; pub:
;     04:5d:1a:4f:d9:bd:49:9e:e4:fd:55:2c:0d:ea:6d:
;     b1:66:64:7a:71:91:13:63:86:fe:ca:94:d4:47:51:
;     39:66:ff:43:d5:62:de:f2:f2:41:3c:2e:3f:95:18:
;     2d:23:f7:e7:8e:75:19:3b:c6:50:fb:d9:90:f5:e8:
;     12:b7:b8:6a:43
; ASN1 OID: prime256v1
; NIST CURVE: P-256
; writing EC key
; -----BEGIN PUBLIC KEY-----
; MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEXRpP2b1JnuT9VSwN6m2xZmR6cZET
; Y4b+ypTUR1E5Zv9D1WLe8vJBPC4/lRgtI/fnjnUZO8ZQ+9mQ9egSt7hqQw==
; -----END PUBLIC KEY-----

; The public key is shown in two different formats.
; The first is this:

; pub:
;     04:5d:1a:4f:d9:bd:49:9e:e4:fd:55:2c:0d:ea:6d:
;     b1:66:64:7a:71:91:13:63:86:fe:ca:94:d4:47:51:
;     39:66:ff:43:d5:62:de:f2:f2:41:3c:2e:3f:95:18:
;     2d:23:f7:e7:8e:75:19:3b:c6:50:fb:d9:90:f5:e8:
;     12:b7:b8:6a:43

; It is the ANSI X9.63 format.
; 65-bytes are the uncompressed public key (04 || X || Y) 

; This is the same public key, but in PEM format

; -----BEGIN PUBLIC KEY-----
; MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEXRpP2b1JnuT9VSwN6m2xZmR6cZET
; Y4b+ypTUR1E5Zv9D1WLe8vJBPC4/lRgtI/fnjnUZO8ZQ+9mQ9egSt7hqQw==
; -----END PUBLIC KEY-----

; It contains ASN.1 that more explicitly identifies the key type.
; 
; SEQUENCE (2 elem)
;   SEQUENCE (2 elem)
;     OBJECT IDENTIFIER 1.2.840.10045.2.1 ecPublicKey (ANSI X9.62 public key type)
;     OBJECT IDENTIFIER 1.2.840.10045.3.1.7 prime256v1 (ANSI X9.62 named elliptic curve)
;   BIT STRING (520 bit) 000001000101110100011010010011111101100110111101010010011001111011100...

Local $bSuccess

; PEM format can be loaded into a Chilkat public key object like this:

$oSbPem = ObjCreate("Chilkat.StringBuilder")
$oSbPem.Append("-----BEGIN PUBLIC KEY-----" & @CRLF)
$oSbPem.Append("MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEXRpP2b1JnuT9VSwN6m2xZmR6cZET" & @CRLF)
$oSbPem.Append("Y4b+ypTUR1E5Zv9D1WLe8vJBPC4/lRgtI/fnjnUZO8ZQ+9mQ9egSt7hqQw==" & @CRLF)
$oSbPem.Append("-----END PUBLIC KEY-----" & @CRLF)

$oPubKey1 = ObjCreate("Chilkat.PublicKey")
$bSuccess = $oPubKey1.LoadFromString($oSbPem.GetAsString())
If ($bSuccess = False) Then
    ConsoleWrite($oPubKey1.LastErrorText & @CRLF)
    Exit
EndIf

; The X9.63 format can be loaded like this:
$oSbHex = ObjCreate("Chilkat.StringBuilder")
$oSbHex.Append("04:5d:1a:4f:d9:bd:49:9e:e4:fd:55:2c:0d:ea:6d:")
$oSbHex.Append("b1:66:64:7a:71:91:13:63:86:fe:ca:94:d4:47:51:")
$oSbHex.Append("39:66:ff:43:d5:62:de:f2:f2:41:3c:2e:3f:95:18:")
$oSbHex.Append("2d:23:f7:e7:8e:75:19:3b:c6:50:fb:d9:90:f5:e8:")
$oSbHex.Append("12:b7:b8:6a:43")

; Get rid of the ":" chars.
Local $iNumReplaced = $oSbHex.Replace(":","")

; We'll need to convert hex to base64..
$oBdKey = ObjCreate("Chilkat.BinData")
$oBdKey.AppendEncoded($oSbHex.GetAsString(),"hex")

$oPubKey2 = ObjCreate("Chilkat.PublicKey")
$bSuccess = $oPubKey2.LoadFromString($oBdKey.GetEncoded("base64"))
If ($bSuccess = False) Then
    ConsoleWrite($oPubKey2.LastErrorText & @CRLF)
    Exit
EndIf

; Let's get the key in pubKey2 as PEM.
; It should be idential to the PEM above.
ConsoleWrite($oPubKey2.GetPem(True) & @CRLF)

; Here's the output.  You can see it's the same as the PEM above..

; -----BEGIN PUBLIC KEY-----
; MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEXRpP2b1JnuT9VSwN6m2xZmR6cZET
; Y4b+ypTUR1E5Zv9D1WLe8vJBPC4/lRgtI/fnjnUZO8ZQ+9mQ9egSt7hqQw==
; -----END PUBLIC KEY-----