package main

import (
	"encoding/hex"
	"github.com/piotrnar/gocoin/btc"
	"log"
)

func main() {
	encryptedKey := "6PfMxA1n3cqYarHoDqPRPLpBBJGWLDY1qX94z8Qyjg7XAMNZJMvHLqAMyS"

	dec := btc.Decodeb58(encryptedKey)[:39] // trim to length 39 (not sure why needed)
	if dec == nil {
		log.Fatal("Cannot decode base58 string " + encryptedKey)
	}

	log.Printf("Decoded base58 string to %s (length %d)", hex.EncodeToString(dec), len(dec))

	if dec[0] == 0x01 && dec[1] == 0x42 {
		log.Printf("EC multiply mode not used")

	} else if dec[0] == 0x01 && dec[1] == 0x43 {
		log.Printf("EC multiply mode used")

	} else {
		log.Fatal("Malformed byte slice")
	}
}

package main

import (
	"encoding/hex"
	"github.com/piotrnar/gocoin/btc"
	"log"
)

func main() {
	encryptedKey := "6PfMxA1n3cqYarHoDqPRPLpBBJGWLDY1qX94z8Qyjg7XAMNZJMvHLqAMyS"

	dec := btc.Decodeb58(encryptedKey)[:39] // trim to length 39 (not sure why needed)
	if dec == nil {
		log.Fatal("Cannot decode base58 string " + encryptedKey)
	}

	log.Printf("Decoded base58 string to %s (length %d)", hex.EncodeToString(dec), len(dec))
}

--- 
+++ 
@@ -15,4 +15,14 @@
 	}
 
 	log.Printf("Decoded base58 string to %s (length %d)", hex.EncodeToString(dec), len(dec))
+
+	if dec[0] == 0x01 && dec[1] == 0x42 {
+		log.Printf("EC multiply mode not used")
+
+	} else if dec[0] == 0x01 && dec[1] == 0x43 {
+		log.Printf("EC multiply mode used")
+
+	} else {
+		log.Fatal("Malformed byte slice")
+	}
 }
Add control flow for different cases
