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package main | |
import ( | |
"crypto/hmac" | |
"crypto/sha1" | |
"encoding/base32" | |
"encoding/binary" | |
"fmt" | |
"math" | |
"time" | |
) | |
func generate_topt(secret string, interval int64, digits int) (string, error) { | |
key, err := base32.StdEncoding.DecodeString(secret) | |
if err != nil { | |
return "", fmt.Errorf("failed to decode secret: %w", err) | |
} | |
time_step := time.Now().Unix() / interval | |
var counter_bytes [8]byte | |
binary.BigEndian.PutUint64(counter_bytes[:], uint64(time_step)) | |
hmac_hash := hmac.New(sha1.New, key) | |
if _, err := hmac_hash.Write(counter_bytes[:]); err != nil { | |
return "", fmt.Errorf("failed to write HMAC: %w", err) | |
} | |
hash := hmac_hash.Sum(nil) | |
offset := hash[len(hash)-1] & 0x0F | |
code := (int(hash[offset])&0x7F)<<24 | | |
(int(hash[offset+1])&0xFF)<<16 | | |
(int(hash[offset+2])&0xFF)<<8 | | |
(int(hash[offset+3]) & 0xFF) | |
otp := code % int(math.Pow10(digits)) | |
return fmt.Sprintf("%0*d", digits, otp), nil | |
} | |
func main() { | |
// secret key | |
secret := "JBSWY3DPEHPK3PXP" | |
// Generate a 6-digit TOTP with 30-second intervals | |
totp, err := generate_topt(secret, 30, 6) | |
if err != nil { | |
fmt.Println("Error generating TOTP:", err) | |
return | |
} | |
fmt.Println("Your TOTP code is:", totp) | |
} |
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