Why certificates are needed on Android: a complete analysis

A modern smartphone based on Android is not just a device for making calls, but a full-fledged computer that stores your personal data, bank details and access to corporate networks. In the world of digital security, a fundamental element of trust is SSL certificates. Many users are faced with the need to install them when connecting to work networks, using specific applications or setting up secure proxies, but few understand the real mechanics of this process.

Essentially, a certificate is a digital passport that confirms the authenticity of the server with which your device communicates. Without this check, you risk handing over your passwords to scammers who have created a fake access point. In this article, we will take a closer look at why the operating system requires verification of the authority of publishers and how to properly manage credential storage.

The issue of connection security becomes critical when you use public Wi-Fi in a cafe or airport. It is at such moments that the verification mechanism digital signature comes into operation, checking the encryption keys. If the chain of trust is broken, the browser or application will immediately warn you of the danger, blocking the transfer of data.

The principle of digital identities in the mobile OS

When you open a site with the protocol HTTPS, your smartphone initiates the process “handshakes” with a remote server. The server sends its certificate containing the public key and owner information. The operating system automatically checks this document against the list of trusted root certification authorities (CAs) that are preinstalled on the system. If the certificate is signed by a known authority, the connection is established without user intervention. However, if you are trying to connect to an internal company resource or are using traffic capture for debugging, the system will not find the signature in its list. In this case, manual installation of Android This document automatically checks against the list of trusted root certification authorities (CAs) that are preinstalled on the system.

If the certificate is signed by a known authority, the connection is established without user intervention. However, if you are trying to connect to an internal company resource or are using traffic capture for debugging, the system will not find the signature in its list. In this case, manual installation is required The verification process occurs at the level of the system kernel and network stack. This means that even if the application has not implemented its own security checks, the operating system will block the insecure connection. a root certificate is required in the device storage

The verification process occurs at the level of the system kernel and network stack. This means that even if the application has not implemented its own security checks, the operating system will block the insecure connection. Having an installed root certificate makes the device vulnerable to man-in-the-middle attacks if this certificate falls into the hands of attackers.

Application developers often use their own certificate authorities to test APIs. In such cases, the developer's phone must have the appropriate root of trust installed, otherwise requests will be rejected with an error SSLHandshakeException.

Main scenarios for using third-party certificates

There are several specific situations when an ordinary user or system administrator has to interact with security settings. Most often this is due to the corporate environment or the specific requirements of network equipment.

• 🏢 Corporate networks and Wi-Fi: Many companies use the WPA2-Enterprise standard with authentication through a RADIUS server. To connect to such Wi-Fi, you often need to install a corporate CA certificate so that the phone trusts the authentication server.
• 🛡️ Antiviruses and firewalls: Applications like Kaspersky or AdGuard can filter HTTPS traffic to block ads or viruses. To do this, they create a local proxy and require the installation of their root certificate.
• 📱 Debugging and development: Programmers use tools like Charles Proxy or Mitmproxy to analyze the network requests of their applications, which is impossible without embedding their certificate in the chain of trust.

At home, the average user rarely has to deal with manual installation. A standard set of certificates, supplied with Google Play Services and updated through the app store, covers 99% of the needs for safe surfing.

However, if you use specific VPN services or connect to a smart home with a local gateway that has a self-signed certificate, the system will constantly issue security warnings until you add an exception.

The process of installing and managing the storage

Installing a certificate on Android is a non-trivial procedure and depends on the version of the operating system. Starting from Android 11 and especially in Android 12/13/14, Google has tightened its security policies, dividing storage into system and user.

To install a file with the extension .crt or .cer you need to go to the security settings. The path may differ depending on the manufacturer's shell, but usually it looks like this: Settings → Security → Encryption and credentials → Install from storage. The system will ask you to set a PIN code or pattern to protect the storage.

After installation, the certificate goes into the user storage. Applications can see its presence, but not all systems trust user roots by default. For example, the browser Chrome on newer versions of Android may ignore custom CAs for major sites, relying only on the system store.

⚠️ Warning: On devices running Android 7.0 and higher, applications do not trust custom certificates by default. To debug HTTPS traffic in such applications, you need to modify the network configuration (network_security_config) or have root access to move the certificate to the system partition.

Removing unnecessary certificates is an important security hygiene procedure. Go to the Settings → Security → Removing credentialssection to clear all user certificates at once, or go to the list of trusted certificates for selective removal.

Differences between system and user certificates

Understanding The difference between these two types of storage is critical to assessing the security level of your device. System certificates are installed by the device manufacturer or updated through the mechanism Google Play System Update.

Characteristics	System certificates	User certificates
Installation source	Manufacturer / Google	Manual installation by the user
Trust level	Full (for all applications)	Limited (depending on the application)
Delete	Only from root access	Available in settings
Risk of compromise	Minimal	High when installing malware

User certificates are stored in encrypted form and protected by lock screen password. If you reset your phone to factory settings, all user certificates will be permanently deleted, requiring you to reinstall them.

Why can't apps see my certificate?

Starting with Android 7.0, apps ignore user certificates for security reasons. In order for an application (for example, for testing) to see your certificate, the developer must explicitly allow this in the application manifest, or you need to move the certificate to the system partition via Root access.

The system storage contains hundreds of certificates from major global certification authorities (DigiCert, Let's Encrypt, GlobalSign, etc.). This list is updated automatically, ensuring that your protection is up to date without user intervention.

Security risks and potential threats

Installing an extra root certificate is like giving the master key to your home to a stranger. If an attacker convinces you to install his certificate (for example, under the guise of updating a driver or bonus app), he will be able to decrypt all your HTTPS traffic.

This allows you to intercept passwords from social networks, messages in instant messengers (if end-end encryption with key verification is not used) and bank card data. Malware often uses this attack vector to infiltrate a secure communication channel.

Certificates installed to work with free VPN services of dubious origin are especially dangerous. Such services can legally (with your permission received when installing the certificate) conduct deep packet analysis (DPI) and sell your data to advertisers.

⚠️ Attention: Regularly check the list of trusted certificates in the settings. If you see a certificate with a name that is unfamiliar to you or that has recently appeared without your knowledge, delete it immediately.

Corporate security policies (MDM) often require the installation of certificates to monitor employee traffic. In this case, you must be aware that the employer has the technical ability to see your traffic inside the corporate network.

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The main rule of security: trust only those root certificates, the source of which is absolutely clear to you and necessary to perform a specific task.

Diagnostics of connection problems and SSL errors

Often users encounter errors like “Your connection is not secure” or “Certificate error”. This can happen for several reasons: an incorrect date on the device, an expired site certificate, or the absence of the required root certificate.

First, check the date and time in the settings System → Date and time. If the clock is slow or fast, the certificate validity check will fail, since the system will consider the current certificate either not yet active or already expired.

For advanced users, it is possible to view certificate details directly in the browser. By clicking on the padlock icon in the address bar, you can see the certification path and check which authority issued the document. If there is an unknown authority in the chain, this is a cause for concern.

In some cases, clearing the SSL cache helps. This can be done through the developer menu or in the settings of a specific browser. The command to reset via ADB is as follows:

adb shell pm clear com.android.chrome

If the problem occurs in only one application, it may be using its own certificate store (Certificate Pinning). In this case, installing a system certificate will not help, and you will need to update the application itself or contact its developer.

What to do if the phone says “Certificate is not trusted”?

First check the date and time. If they are correct, try opening the site in a different browser. If the problem is everywhere, your ISP or antivirus may be intercepting traffic. Try disabling your VPN or antivirus for a while. If the site is a corporate site, contact your system administrator for the current root certificate.

Is it possible to disable certificate checking completely?

Technically, this is possible through the developer settings (“Do not check SSL certificates”), but doing this is strictly not recommended. This disables protection for all applications and leaves the device open to any attacks on the network. Use this option only on an isolated test device.

Where are certificates physically stored in Android?

System certificates are located in the /system/etc/security/cacertssection. User certificates are stored in an encrypted Keystore, access to which is protected by a screen unlock password and is tied to a specific device user.

Does installing a certificate affect the speed of the phone?

The very fact of having a certificate in the store does not affect performance. However, the process of verifying the chain of trust on every HTTPS connection is computationally expensive. On modern processors, this delay is milliseconds and is invisible to the user.