diff --git a/main.go b/main.go
index ccfa8a4..17e4e78 100644
--- a/main.go
+++ b/main.go
@@ -1,96 +1,161 @@
 package main
 
+/*
+based on
+https://github.com/ipfs/go-ipfs-keystore/blob/master/keystore.go
+https://github.com/ipfs/go-ipfs/blob/master/core/coreapi/key.go
+https://github.com/ipfs/go-ipfs/blob/master/core/node/identity.go
+*/
+
 import (
 	"crypto/rand"
 	"fmt"
-	"io/ioutil"
 	"log"
 	"os"
 	"regexp"
 	"runtime"
-	"strings"
+	//"strings"
+	"encoding/base64"
+	//"encoding/base32"
 
 	"github.com/libp2p/go-libp2p-core/crypto"
 	"github.com/libp2p/go-libp2p-core/peer"
 )
 
 var (
-	alphabet   = regexp.MustCompile("^[123456789abcdefghijklmnopqrstuvwxyz]+$")
 	numWorkers = runtime.NumCPU()
 )
 
 // Key stores PrettyID containing desired substring at Index
 type Key struct {
 	PrettyID string
-	Index    int
+	Index int
+	Part string
+	PrivateKey64 string
 }
 
 func main() {
 	if len(os.Args) != 2 {
 		fmt.Printf(`
-This tool generates IPFS public and private keypair until it finds public key
-which contains required substring. Keys are stored in local directory. If you
-like one of them, you can move it to ~/.ipfs/keystore/ to use it with IPFS.
+This tool can generate IPFS public and private keypairs
+and filter the public keys by regex, to find vanity IPFS public keys
+
+Keypairs are printed to stdout and to output.txt
+
+To use a key, edit your ~/.ipfs/config file, which is generated by ipfs init
+Identity.PeerID is your public key
+Identity.PrivKey is your private key in base64 encoding
 
 Usage:
-	%s {part}
-		For fast results suggested length of public key part is 4-5 characters
+  %s {regex}
+  For fast results, use a short substring of 4-5 characters
+
+Alphabet of public key:
+  [1-9a-zA-Z]
+
+Regex samples:
+  hello$
+  (?i)hello
+  (foo|bar)$
+
+Regex basics:
+  (?i)  add this prefix to make the regex case-insensitive
+  (a|b)  a or b
+  $  end of string
+  ^  start of string. not needed here, the start is mostly constant
+
+Regex docs:
+  https://duckduckgo.com/?q=golang+regexp
+  https://yourbasic.org/golang/regexp-cheat-sheet/
+  https://golangdocs.com/regex-in-golang-regexp-package
+
 `, os.Args[0])
 		os.Exit(1)
 	}
-	part := strings.ToLower(os.Args[1])
-	if !alphabet.MatchString(part) {
-		fmt.Println("{part} must match the alphabet:", alphabet.String())
-		os.Exit(2)
+
+	partRegex := regexp.MustCompile(os.Args[1])
+	// TODO? validate regex with alphabet
+	//alphabet = regexp.MustCompile("^[123456789abcdefghijklmnopqrstuvwxyz]+$")
+
+	outputFile, err := os.OpenFile("output.txt", os.O_APPEND | os.O_CREATE | os.O_WRONLY, 0644)
+	if err != nil {
+		log.Println(err)
 	}
+	defer outputFile.Close()
+
 	runtime.GOMAXPROCS(numWorkers)
 	keyChan := make(chan Key)
 	for i := 0; i < numWorkers; i++ {
 		go func() {
-			err := generateKey(part, keyChan)
+			err := generateKey(partRegex, keyChan)
 			if err != nil {
 				log.Fatal(err)
 			}
 		}()
 	}
 	for key := range keyChan {
+
 		fmt.Printf(
-			"%s\u001b[32m%s\u001b[0m%s\n",
+			// TODO allow to disable color
+			"%s %s\u001b[32m%s\u001b[0m%s %s\n",
+			//"%s %s%s%s %s\n",
+			key.Part,
 			key.PrettyID[:key.Index],
-			key.PrettyID[key.Index:len(part)+key.Index],
-			key.PrettyID[len(part)+key.Index:])
+			key.PrettyID[key.Index:len(key.Part)+key.Index],
+			key.PrettyID[len(key.Part)+key.Index:],
+			key.PrivateKey64,
+		)
 
+		// TODO allow to print json format for ~/.ipfs/config
+		/*
+		fmt.Printf(
+			"%s\n  \"Identity\": {\n    \"PeerID\": \"%s\",\n    \"PrivKey\": \"%s\",\n  },\n\n",
+			key.Part, key.PrettyID, key.PrivateKey64,
+		)
+		*/
+
+		// TODO allow to disable writing to output.txt
+		_, err := outputFile.WriteString(
+			fmt.Sprintf("%s %s %s\n", key.Part, key.PrettyID, key.PrivateKey64),
+		)
+		if err != nil {
+			log.Println(err)
+		}
 	}
 }
 
-func generateKey(part string, keyChan chan Key) error {
+func generateKey(partRegex *regexp.Regexp, keyChan chan Key) error {
 	for {
 		privateKey, publicKey, err := crypto.GenerateEd25519Key(rand.Reader)
 		if err != nil {
 			return err
 		}
+
 		peerID, err := peer.IDFromPublicKey(publicKey)
 		if err != nil {
 			return err
 		}
 		prettyID := peerID.Pretty()
-		lowerID := strings.ToLower(prettyID)
-		idx := strings.Index(lowerID, part)
-		if idx == -1 {
+
+		if !partRegex.MatchString(prettyID) {
 			continue
 		}
-		privateKeyBytes, err := privateKey.Raw()
-		if err != nil {
-			return err
-		}
-		err = ioutil.WriteFile(prettyID, privateKeyBytes, 0600)
-		// TODO print privateKey in base64, as in ~/.ipfs/config .Identity.PrivKey
+
+		part := partRegex.FindString(prettyID)
+		idx := partRegex.FindStringIndex(prettyID)[0]
+
+		privateKeyBytes, err := crypto.MarshalPrivateKey(privateKey)
 		if err != nil {
 			return err
 		}
+
+		privateKey64 := base64.StdEncoding.EncodeToString(privateKeyBytes)
+
 		keyChan <- Key{
 			PrettyID: prettyID,
 			Index:    idx,
+			Part:     part,
+			PrivateKey64: privateKey64,
 		}
 	}
 }