Android APK Signing & Certificate Analyzer
Analyze Android APK files to detect signing schemes (v1/v2/v3), extract X.509 certificates from signature blocks, verify certificate validity, check for tampering indicators, and explore APK file structure. Free, private, and no signup required.
Analyze Android APK files for signing scheme versions (v1/v2/v3), parse X.509 certificates from signature block files, extract issuer and subject details, check certificate validity, detect signature anomalies, and identify potential fakery. All analysis runs locally in your browser - no files are uploaded.
Why Use Our Android APK Signing & Certificate Analyzer?
Instant APK Signature Detection & Analysis
Analyze Android APK files instantly to detect all signing schemes: v1 (JAR signing via META-INF/MANIFEST.MF, CERT.SF, CERT.RSA), v2 (APK Signature Scheme block before Central Directory), and v3 (signature block with signer sequence). Identify which schemes are present with detailed descriptions and block sizes.
Secure & Private Certificate Analysis
All APK analysis happens entirely in your browser. Your APK files, extracted certificates, and analysis results never leave your device. No data uploaded, no tracking, no signup required - complete privacy for analyzing sensitive APK files.
APK Analysis Online - No Installation
Use the APK signing analyzer directly in any modern browser with no downloads, apps, or tools required. Features file upload with drag-and-drop, auto-parse of ZIP/APK structure, signature scheme detection, X.509 certificate parsing with subject/issuer details, validity checking, and full file content listing.
Comprehensive Certificate & Integrity Analysis
Our analyzer extracts and parses X.509 certificates from APK signature blocks: subject and issuer distinguished names with common attributes (CN, O, OU, C), certificate validity period with remaining days, serial number, version, signature algorithm, public key algorithm and size, self-signed detection, and comprehensive integrity warnings for missing or anomalous signatures.
Common Use Cases for Android APK Signing & Certificate Analyzer
Malware Analysis & APK Triage
Security analysts use the APK signing analyzer to quickly triage suspicious Android applications during malware analysis. Missing or anomalous signatures, self-signed certificates with unusual subject names, and expired certificates are common indicators of potentially malicious APKs that warrant further investigation.
APK Integrity & Authenticity Verification
Security auditors verify the signing integrity of APK files before sideloading or distribution. The tool checks that proper v1/v2/v3 signature schemes are present, extracts certificate details for identity verification, and flags tampering indicators such as missing META-INF files or incomplete signature chains.
Android App Development & Debugging
Android developers use the signing analyzer to verify their APK build outputs. Validate that the correct signing certificate was used, check expiration dates on release keys, ensure both v1 and v2/v3 schemes are present for compatibility, and verify that debug builds are properly identified.
Learning APK Structure & Signing
Students learning about Android application packaging and security use the analyzer to explore real APK structure. The file listing reveals the complete ZIP contents including AndroidManifest.xml, classes.dex, resources, and META-INF signature files. Certificate parsing demonstrates X.509 certificate anatomy in practice.
App Store & Marketplace Vetting
App store reviewers and marketplace operators use signature analysis to vet submitted APKs. The tool helps verify that apps are properly signed, certificates are valid and not expired, and that signature schemes meet store requirements. Anomalous signing patterns can flag potentially fraudulent uploads.
Digital Forensics & Evidence Analysis
Digital forensics investigators analyze APK files recovered from devices during investigations. The signing analyzer helps establish the origin and authenticity of recovered APKs by extracting certificate details, identifying the signer, and checking for tampering or repackaging indicators.
Understanding APK Signing & Certificate Analysis
What is APK Signing?
APK signing is the process of digitally signing an Android application package to verify its authenticity and integrity. Every APK must be signed before it can be installed on an Android device or published on Google Play. The signature ensures that the APK has not been tampered with since it was signed and identifies the developer who created it. Android supports three signing schemes: v1 (JAR signing) based on PKCS7 signed data in META-INF/, v2 (APK Signature Scheme v2) which signs the entire APK before the Central Directory for faster verification, and v3 (APK Signature Scheme v3) which adds support for key rotation.
Our APK Signing & Certificate Analyzer parses APK files to detect which signing schemes are present, extracts X.509 certificates from signature block files, and displays certificate details including issuer, subject, validity period, public key information, and self-signed status. The tool also provides a complete file listing of the APK contents and flags potential integrity issues. All processing runs locally in your browser with no file uploads to any server.
How Our APK Signing Analyzer Works
- 1. APK File Loading & Structure Parsing: Drag and drop or browse to select an APK file. The tool reads the ZIP structure by locating the End of Central Directory (EOCD) record at the end of the file, then parses the Central Directory to enumerate all files within the APK. Files in the META-INF/ directory (MANIFEST.MF, CERT.SF, CERT.RSA) and key APK components (AndroidManifest.xml, classes.dex) are highlighted for easy identification.
- 2. Signature Scheme Detection: The engine checks for all three signing schemes: v1 JAR signing by looking for META-INF/MANIFEST.MF, CERT.SF, and CERT.RSA signature block files in the ZIP directory; v2/v3 APK Signature Scheme by scanning for the APK Signing Block between the ZIP content and the Central Directory (identified by the "APK Sig Block 42" magic marker). Each detected scheme is reported with a description and relevant details.
- 3. X.509 Certificate Extraction & Parsing: If a CERT.RSA or CERT.DSA file is found in META-INF/, the tool extracts the PKCS#7 SignedData structure and locates the embedded X.509 certificate using ASN.1 DER parsing. The certificate is decoded to extract: subject and issuer distinguished names (CN, O, OU, C, L, ST), validity period with date range checking, serial number, signature algorithm, public key algorithm and estimated key size, certificate version, and self-signed status. SHA-256 and SHA-1 fingerprints are computed using the Web Crypto API.
APK Signature Schemes Explained
- v1 (JAR Signing): The original Android signing scheme based on standard JAR signing. It uses META-INF/MANIFEST.MF (list of all files with their SHA-1 digests), META-INF/CERT.SF (digests of MANIFEST.MF entries signed by the certificate), and META-INF/CERT.RSA (PKCS7 SignedData containing the X.509 certificate and signature). This scheme signs individual files rather than the entire APK, which means some content can be added or removed without invalidating the signature.
- v2 (APK Signature Scheme v2): Introduced in Android 7.0 (API level 24), this scheme signs the entire APK before the ZIP Central Directory using a signing block that contains signer sequences with digests covering the complete APK content. The signature is verified before any ZIP processing, providing stronger integrity guarantees. The signing block is inserted between the ZIP content and the Central Directory.
- v3 (APK Signature Scheme v3): Introduced in Android 9.0 (API level 28), this scheme extends v2 with support for key rotation. It uses the same signing block structure as v2 but includes additional proof-of-rotation data that allows the app signing key to be changed over time while maintaining a chain of trust. The verifier can trace back through previous signing keys to establish continuity.
- Fakery Detection: The analyzer checks for several tampering indicators: missing AndroidManifest.xml, absence of classes.dex files, incomplete signature file sets (MANIFEST.MF without corresponding CERT.SF or CERT.RSA), unusual file entries that may indicate repackaging, and self-signed certificates with suspicious subject names. These checks help identify potentially modified or fraudulent APKs.
Privacy, Security & Availability
The Android APK Signing & Certificate Analyzer is 100% free with no signup required. All APK analysis is performedlocally in your browser using client-side JavaScript - your APK files, extracted certificates, and analysis reportsnever leave your device. There areno usage limits or rate caps. The tool supports APK files up to 50MB for analysis, covers all three signing schemes (v1/v2/v3), parses X.509 certificates from PKCS7 signature blocks, provides detailed file content listing, and flags integrity and tampering indicators. Use it as many times as you need for security analysis, development verification, or education.
Frequently Asked Questions About Android APK Signing & Certificate Analyzer
APK signing is a cryptographic process that ensures an Android application package (APK) has not been tampered with and was signed by a known developer. Every APK must be signed before installation on an Android device or publication on Google Play. The digital signature binds the developer identity to the APK and detects any modification to the package contents after signing. Android verifies the signature during installation to prevent running modified or malicious code.
v1 (JAR signing) signs individual files using META-INF/MANIFEST.MF and CERT.SF/RSA files. It is the most compatible but allows file addition/removal without invalidating the signature. v2 (APK Signature Scheme v2), introduced in Android 7.0, signs the entire APK using a signing block before the ZIP Central Directory for stronger integrity. v3 (APK Signature Scheme v3), introduced in Android 9.0, extends v2 with key rotation support, allowing developers to change their signing key while maintaining a chain of trust.
The tool scans the APK for the APK Signing Block, which is located immediately before the ZIP Central Directory. This block is identified by the "APK Sig Block 42" magic marker (a 16-byte sequence). When found, the tool reports the signing block presence and its size. Distinguishing between v2 and v3 requires examining the signer sequence contents, which the tool detects as a combined v2/v3 presence.
No. This tool is a read-only analyzer that inspects and reports on existing APK signatures. It does not create, modify, or remove signatures. For signing APKs, you need the Android SDK tools (apksigner, jarsigner) or Android Studio. Our tool is designed for verification, analysis, and educational purposes only.
Absolutely. The APK Signing & Certificate Analyzer runs entirely in your browser. Your APK files, extracted certificate details, and analysis results are never uploaded to any server, stored in a database, or tracked in any way. All processing, including ZIP structure parsing and X.509 certificate decoding, happens locally on your device - nothing leaves your computer. No signup required.
The tool extracts comprehensive certificate details from APK signature block files: subject distinguished name (CN, O, OU, C, L, ST), issuer distinguished name, certificate serial number, validity period (not before and not after dates with remaining days calculation), signature algorithm (e.g., SHA-256 with RSA), public key algorithm (RSA, EC, DSA), estimated key size in bits, certificate version (v1/v2/v3), and self-signed status. Certificate identifiers like version and serial number are also displayed.
A self-signed certificate has the same subject and issuer, meaning the certificate signed itself rather than being signed by a recognized Certificate Authority (CA). Most Android app signing certificates are self-signed - developers generate their own key pairs for signing. This is normal and expected for app distribution. However, self-signed certificates with suspicious or unusual subject names can be a red flag in malware analysis.
The tool flags several tampering indicators: missing AndroidManifest.xml (the APK may be malformed), absence of classes.dex files (no executable code), incomplete META-INF signature file sets (e.g., MANIFEST.MF without CERT.SF or CERT.RSA), unusual or unfamiliar file entries that suggest repackaging, expired certificates, and certificates with suspicious subject names. Multiple warnings together suggest a higher likelihood of tampering.
Yes - the Android APK Signing & Certificate Analyzer is 100% free with no signup, no account, and no usage limits. Analyze any APK file as many times as you need, completely free forever. There are no hidden charges, premium tiers, or usage caps of any kind.