[Tutorial] How to generate a custom signing key (.pem) using OpenSSL
[Tutorial] How to generate a custom signing key (.pem) using OpenSSL
12-03-2020, 07:20 PM
This guide will explain how to generate a custom key which can be used to sign your Android images like boot, recovery, system etc. This guide will come in handy in a case where the bootloader only accepts signed images (whether self-signed or factory-signed).
Requirements
- A PC (I'm using Windows for this guide)
- Download and install OpenSSL Light for Windows @ https://slproweb.com/products/Win32OpenSSL.html
Steps to create a custom signing key using OpenSSL
Follow the steps below to generate a custom private key
See the video tutorial below or @ https://youtu.be/uICvoalIUf8- Tap the Start menu and search for cmd.exe
![[Image: How-to-generate-a-custom-signing-key-1.png]](https://www.hovatek.com/blog/bpyeki/uploads/2020/03/How-to-generate-a-custom-signing-key-1.png)
- Right-click CMD from the results and run as Administrator
![[Image: How-to-generate-a-custom-signing-key-2.png]](https://www.hovatek.com/blog/bpyeki/uploads/2020/03/How-to-generate-a-custom-signing-key-2.png)
- Click Yes when prompted
- Open the directory where OpenSSL was installed to and open the bin folder (mine is C:\Program Files\OpenSSL-Win64\bin . Ensure to enter yours in the command below)
![[Image: How-to-generate-a-custom-signing-key-3.png]](https://www.hovatek.com/blog/bpyeki/uploads/2020/03/How-to-generate-a-custom-signing-key-3.png)
- Right-click the address bar and select Copy address
![[Image: How-to-generate-a-custom-signing-key-4.png]](https://www.hovatek.com/blog/bpyeki/uploads/2020/03/How-to-generate-a-custom-signing-key-4.png)
- Go back to command prompt, type this command (use your own location) and tap Enter
Code:cd C:\Program Files\OpenSSL-Win64\bin
![[Image: How-to-generate-a-custom-signing-key-5.png]](https://www.hovatek.com/blog/bpyeki/uploads/2020/03/How-to-generate-a-custom-signing-key-5.png)
- You should now be in the C:\Program Files\OpenSSL-Win64\bin at command prompt
![[Image: How-to-generate-a-custom-signing-key-6.png]](https://www.hovatek.com/blog/bpyeki/uploads/2020/03/How-to-generate-a-custom-signing-key-6.png)
- Type this command (I've chosen to name my key hovatek) and tap Enter
Code:openssl genrsa -f4 -out hovatek.pem 4096
![[Image: How-to-generate-a-custom-signing-key-7.png]](https://www.hovatek.com/blog/bpyeki/uploads/2020/03/How-to-generate-a-custom-signing-key-7.png)
- Wait till its done (i.e back to C:\Program Files\OpenSSL-Win64\bin>_)
![[Image: How-to-generate-a-custom-signing-key-8.png]](https://www.hovatek.com/blog/bpyeki/uploads/2020/03/How-to-generate-a-custom-signing-key-8.png)
- You should now find a hovatek.pem file
![[Image: How-to-generate-a-custom-signing-key-9.png]](https://www.hovatek.com/blog/bpyeki/uploads/2020/03/How-to-generate-a-custom-signing-key-9.png)
Important Notice
- Your OpenSSL installation directory might vary from mine so ensure to enter yours
- The generated .pem file is a custom one and very likely to be different from what your device's OEM uses to sign its images
This post was last modified: 12-03-2020, 08:42 PM by hovatek.
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07-09-2021, 11:45 AM
(07-09-2021, 04:44 AM)nheaven Why I can't get a .pem file after running OpenSSL in the bin folder?
depends on the folder path where you ran the openssl command and what command you sent
you should upload a screenshot showing your cmd prompt window
Learn MediaTek, Unisoc / Spreadtrum (SPD) and Qualcomm Software Repairs @ https://www.hovatek.com/training
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07-09-2021, 08:27 PM
(07-09-2021, 11:45 AM)X3non(07-09-2021, 04:44 AM)nheaven Why I can't get a .pem file after running OpenSSL in the bin folder?
depends on the folder path where you ran the openssl command and what command you sent
you should upload a screenshot showing your cmd prompt window
I can get the output in Linux, but not in windows 7
12-01-2023, 10:50 AM
(07-09-2021, 11:45 AM)X3nonyou can just add it to path in environmentalal variables(07-09-2021, 04:44 AM)nheaven Why I can't get a .pem file after running OpenSSL in the bin folder?
depends on the folder path where you ran the openssl command and what command you sent
you should upload a screenshot showing your cmd prompt window
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