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Understanding a few ECDSA Public Key Formats
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Describes a few ECDSA public key formats.Chilkat Go Downloads
success := false
// 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:
sbPem := chilkat.NewStringBuilder()
sbPem.Append("-----BEGIN PUBLIC KEY-----\r\n")
sbPem.Append("MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEXRpP2b1JnuT9VSwN6m2xZmR6cZET\r\n")
sbPem.Append("Y4b+ypTUR1E5Zv9D1WLe8vJBPC4/lRgtI/fnjnUZO8ZQ+9mQ9egSt7hqQw==\r\n")
sbPem.Append("-----END PUBLIC KEY-----\r\n")
pubKey1 := chilkat.NewPublicKey()
success = pubKey1.LoadFromString(*sbPem.GetAsString())
if success == false {
fmt.Println(pubKey1.LastErrorText())
sbPem.DisposeStringBuilder()
pubKey1.DisposePublicKey()
return
}
// The X9.63 format can be loaded like this:
sbHex := chilkat.NewStringBuilder()
sbHex.Append("04:5d:1a:4f:d9:bd:49:9e:e4:fd:55:2c:0d:ea:6d:")
sbHex.Append("b1:66:64:7a:71:91:13:63:86:fe:ca:94:d4:47:51:")
sbHex.Append("39:66:ff:43:d5:62:de:f2:f2:41:3c:2e:3f:95:18:")
sbHex.Append("2d:23:f7:e7:8e:75:19:3b:c6:50:fb:d9:90:f5:e8:")
sbHex.Append("12:b7:b8:6a:43")
// Get rid of the ":" chars.
numReplaced := sbHex.Replace(":","")
// We'll need to convert hex to base64..
bdKey := chilkat.NewBinData()
bdKey.AppendEncoded(*sbHex.GetAsString(),"hex")
pubKey2 := chilkat.NewPublicKey()
success = pubKey2.LoadFromString(*bdKey.GetEncoded("base64"))
if success == false {
fmt.Println(pubKey2.LastErrorText())
sbPem.DisposeStringBuilder()
pubKey1.DisposePublicKey()
sbHex.DisposeStringBuilder()
bdKey.DisposeBinData()
pubKey2.DisposePublicKey()
return
}
// Let's get the key in pubKey2 as PEM.
// It should be idential to the PEM above.
fmt.Println(*pubKey2.GetPem(true))
// 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-----
sbPem.DisposeStringBuilder()
pubKey1.DisposePublicKey()
sbHex.DisposeStringBuilder()
bdKey.DisposeBinData()
pubKey2.DisposePublicKey()