Golang : Load ASN1 encoded DSA public key PEM file example
In this tutorial, we will learn how to get the DSA public key from a ASN1 encoded PEM file generated from previous tutorial. Pretty straight forward examples. Hope it helps!
From file :
package main
import (
"bufio"
"crypto/dsa"
"encoding/asn1"
"encoding/pem"
"fmt"
"os"
)
func main() {
//load DSA PEM encoded public key file
pemFile, err := os.Open("DSApublickey.pem")
if err != nil {
fmt.Println(err)
os.Exit(1)
}
// need to convert PEM file to []byte for decoding
pemFileInfo, _ := pemFile.Stat()
var size int64 = pemFileInfo.Size()
pemBytes := make([]byte, size)
// read pemFile content into pemBytes
buffer := bufio.NewReader(pemFile)
_, err = buffer.Read(pemBytes)
// proper decoding now
pemBlock, _ := pem.Decode([]byte(pemBytes))
pemFile.Close()
// convert PEM block to dsa.PublicKey
// we use ASN1 because the PEM block was encoded with ASN1
// see https://www.socketloop.com/tutorials/golang-generate-dsa-private-public-key-and-pem-files-example
// if the PEM block is not encoded by ASN1, the unmarshal will fail
// you need to find out the Public Key algorithm used to encode the PEM bytes
var publicKey dsa.PublicKey
_, err = asn1.Unmarshal(pemBlock.Bytes, &publicKey)
if err != nil {
fmt.Println(err)
os.Exit(1)
}
//fmt.Printf("Public key : \n%x\n", publicKey)
fmt.Printf("Public key parameter P: %v\n", publicKey.Parameters.P)
fmt.Printf("Public key parameter Q: %v\n", publicKey.Parameters.Q)
fmt.Printf("Public key parameter G: %v\n", publicKey.Parameters.G)
fmt.Printf("Public key Y: %v\n", publicKey.Y)
}
and from PEM block :
package main
import (
"crypto/dsa"
"encoding/asn1"
"encoding/pem"
"fmt"
"os"
)
func main() {
var pemBytes = `
-----BEGIN PUBLIC KEY-----
MIIBpjCCAR4CgYEA1cKOQUxDRqRHt8yR5vfEunyFB6pblE9W/fyaJHgpWMzkvSHX
mZvDhN5huH3OM0vC5Y8UbfyplET3x/HfXUbDUgk4bT0CrWHmrANMjdPgStZF+nWP
Yfa6QUyVbRZumI6iBaCH63107scE8tygmwSW3n1jYLoSv6VItDEiBIdoK18CFQC6
q4LlyX4YZblOKYw8CFyPShtcAwKBgHAN+TWyUhqCVZmwUdH3pJelT4iT9vkg4NLn
1h+qJJ1XU+OILAAeuO3z8vLMIpeFaDL5CvUb7S0vSqx2EFj/G67aH9nL0MwtXjn7
SCy4EOF5dlHbafXj4PnPrvo3/Mr+3a2i5lenlhyyb1Vnd/0VcrGwWleAfDBuGdYu
S5WCYAj3AoGBAMDl+N8XI3LBi/LUQbi9di0tvA/2t+c6UZTT/CDTkyDucFNEeqWI
sdOsf+hIbI8pEy81y6yBc50wcf1uqcZxovKsZbuv8vS3NBPaeOT7l6ltYdNxzg/7
QFfi3qQXXLONWYXW4diWaZu6Kq5XvhfWkoUdGzGiD84UVW7jmeDy/Px6
-----END PUBLIC KEY-----
`
// proper decoding now
pemBlock, _ := pem.Decode([]byte(pemBytes))
// convert PEM block to dsa.PublicKey
// we use ASN1 because the PEM block was encoded with ASN1
// see https://www.socketloop.com/tutorials/golang-generate-dsa-private-public-key-and-pem-files-example
// if the PEM block is not encoded by ASN1, the unmarshal will fail
// you need to find out the Public Key algorithm used to encode the PEM bytes
var publicKey dsa.PublicKey
_, err := asn1.Unmarshal(pemBlock.Bytes, &publicKey)
if err != nil {
fmt.Println(err)
os.Exit(1)
}
//fmt.Printf("Public key : \n%x\n", publicKey)
fmt.Printf("Public key parameter P: %v\n", publicKey.Parameters.P)
fmt.Printf("Public key parameter Q: %v\n", publicKey.Parameters.Q)
fmt.Printf("Public key parameter G: %v\n", publicKey.Parameters.G)
fmt.Printf("Public key Y: %v\n", publicKey.Y)
}
See also : Golang : Generate DSA private, public key and PEM files example
By Adam Ng
IF you gain some knowledge or the information here solved your programming problem. Please consider donating to the less fortunate or some charities that you like. Apart from donation, planting trees, volunteering or reducing your carbon footprint will be great too.
Advertisement
Tutorials
+7.9k Golang : Convert octal value to string to deal with leading zero problem
+7.4k Golang : Populate slice with sequential integers example
+10.5k Golang : Validate email address
+18.9k Golang : How to get time zone and load different time zone?
+7k Golang : Find correlation coefficient example
+5.3k Golang : Check if one string(rune) is permutation of another string(rune)
+15.5k Golang : When to use init() function?
+20.5k Golang : How to print rune, unicode, utf-8 and non-ASCII CJK(Chinese/Japanese/Korean) characters?
+31k Golang : Save image to PNG, JPEG or GIF format.
+39k Golang : How to check if a string contains another sub-string?
+6.8k Golang : Progress bar with ∎ character