Visual FoxPro

Understanding a few ECDSA Public Key Formats

See more ECC Examples

Describes a few ECDSA public key formats. Visual FoxPro

LOCAL lnSuccess
LOCAL loSbPem
LOCAL loPubKey1
LOCAL loSbHex
LOCAL lnNumReplaced
LOCAL loBdKey
LOCAL loPubKey2

lnSuccess = 0

* 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...

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

loSbPem = CreateObject('Chilkat.StringBuilder')
loSbPem.Append("-----BEGIN PUBLIC KEY-----" + CHR(13) + CHR(10))
loSbPem.Append("MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEXRpP2b1JnuT9VSwN6m2xZmR6cZET" + CHR(13) + CHR(10))
loSbPem.Append("Y4b+ypTUR1E5Zv9D1WLe8vJBPC4/lRgtI/fnjnUZO8ZQ+9mQ9egSt7hqQw==" + CHR(13) + CHR(10))
loSbPem.Append("-----END PUBLIC KEY-----" + CHR(13) + CHR(10))

loPubKey1 = CreateObject('Chilkat.PublicKey')
lnSuccess = loPubKey1.LoadFromString(loSbPem.GetAsString())
IF (lnSuccess = 0) THEN
    ? loPubKey1.LastErrorText
    RELEASE loSbPem
    RELEASE loPubKey1
    CANCEL
ENDIF

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

* Get rid of the ":" chars.
lnNumReplaced = loSbHex.Replace(":","")

* We'll need to convert hex to base64..
loBdKey = CreateObject('Chilkat.BinData')
loBdKey.AppendEncoded(loSbHex.GetAsString(),"hex")

loPubKey2 = CreateObject('Chilkat.PublicKey')
lnSuccess = loPubKey2.LoadFromString(loBdKey.GetEncoded("base64"))
IF (lnSuccess = 0) THEN
    ? loPubKey2.LastErrorText
    RELEASE loSbPem
    RELEASE loPubKey1
    RELEASE loSbHex
    RELEASE loBdKey
    RELEASE loPubKey2
    CANCEL
ENDIF

* Let's get the key in pubKey2 as PEM.
* It should be idential to the PEM above.
? loPubKey2.GetPem(1)

* 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-----

RELEASE loSbPem
RELEASE loPubKey1
RELEASE loSbHex
RELEASE loBdKey
RELEASE loPubKey2