[android] How do I find out which keystore was used to sign an app?

I have an app which is signed and several keystore files. I'd like to update the app, so I need to find out which one of keys was used.

How can I match which keystore was used to originally sign my app against various keystores I have on my machine?

To build on Paul Lammertsma's answer, this command will print the names and signatures of all APKs in the current dir (I'm using sh because later I need to pipe the output to grep):

find . -name "*.apk" -exec echo "APK: {}" \; -exec sh -c 'keytool -printcert -jarfile "{}"' \;

Sample output:

APK: ./com.google.android.youtube-10.39.54-107954130-minAPI15.apk
Signer #1:

Signature:

Owner: CN=Unknown, OU="Google, Inc", O="Google, Inc", L=Mountain View, ST=CA, C=US
Issuer: CN=Unknown, OU="Google, Inc", O="Google, Inc", L=Mountain View, ST=CA, C=US
Serial number: 4934987e
Valid from: Mon Dec 01 18:07:58 PST 2008 until: Fri Apr 18 19:07:58 PDT 2036
Certificate fingerprints:
         MD5:  D0:46:FC:5D:1F:C3:CD:0E:57:C5:44:40:97:CD:54:49
         SHA1: 24:BB:24:C0:5E:47:E0:AE:FA:68:A5:8A:76:61:79:D9:B6:13:A6:00
         SHA256: 3D:7A:12:23:01:9A:A3:9D:9E:A0:E3:43:6A:B7:C0:89:6B:FB:4F:B6:79:F4:DE:5F:E7:C2:3F:32:6C:8F:99:4A
         Signature algorithm name: MD5withRSA
         Version: 1

APK: ./com.google.android.youtube_10.40.56-108056134_minAPI15_maxAPI22(armeabi-v7a)(480dpi).apk
Signer #1:

Signature:

Owner: CN=Unknown, OU="Google, Inc", O="Google, Inc", L=Mountain View, ST=CA, C=US
Issuer: CN=Unknown, OU="Google, Inc", O="Google, Inc", L=Mountain View, ST=CA, C=US
Serial number: 4934987e
Valid from: Mon Dec 01 18:07:58 PST 2008 until: Fri Apr 18 19:07:58 PDT 2036
Certificate fingerprints:
         MD5:  D0:46:FC:5D:1F:C3:CD:0E:57:C5:44:40:97:CD:54:49
         SHA1: 24:BB:24:C0:5E:47:E0:AE:FA:68:A5:8A:76:61:79:D9:B6:13:A6:00
         SHA256: 3D:7A:12:23:01:9A:A3:9D:9E:A0:E3:43:6A:B7:C0:89:6B:FB:4F:B6:79:F4:DE:5F:E7:C2:3F:32:6C:8F:99:4A
         Signature algorithm name: MD5withRSA
         Version: 1

Or if you just care about SHA1:

find . -name "*.apk" -exec echo "APK: {}" \; -exec sh -c 'keytool -printcert -jarfile "{}" | grep SHA1' \;

Sample output:

APK: ./com.google.android.youtube-10.39.54-107954130-minAPI15.apk
         SHA1: 24:BB:24:C0:5E:47:E0:AE:FA:68:A5:8A:76:61:79:D9:B6:13:A6:00
APK: ./com.google.android.youtube_10.40.56-108056134_minAPI15_maxAPI22(armeabi-v7a)(480dpi).apk
         SHA1: 24:BB:24:C0:5E:47:E0:AE:FA:68:A5:8A:76:61:79:D9:B6:13:A6:00

You can use Java 7's Key and Certificate Management Tool keytool to check the signature of a keystore or an APK without extracting any files.

Signature of an APK or AAB

# APK file
keytool -printcert -jarfile app.apk

# AAB file
keytool -printcert -jarfile app.aab

The output will reveal the signature owner/issuer and MD5, SHA1 and SHA256 fingerprints of the APK file app.apk or AAB file app.aab.

(Note that the -jarfile argument was introduced in Java 7; see the documentation for more details.)

Signature of a keystore

keytool -list -v -keystore release.jks

The output will reveal the aliases (entries) in the keystore file release.jks, with the certificate fingerprints (MD5, SHA1 and SHA256).

If the SHA1 fingerprints between the APK and the keystore match, then you can rest assured that that app is signed with the key.

There are many freewares to examine the certificates and key stores such as KeyStore Explorer.

Unzip the apk and open the META-INF/?.RSA file. ? shall be CERT or ANDROID or may be something else. It will display all the information associated with your apk.

You can do this with the apksigner tool that is part of the Android SDK:

apksigner verify --print-certs my_app.apk

You can find apksigner inside the build-tools directory. For example: ~/Library/Android/sdk/build-tools/29.0.1/apksigner

Much easier way to view the signing certificate:

jarsigner.exe -verbose -verify -certs myapk.apk

This will only show the DN, so if you have two certs with the same DN, you might have to compare by fingerprint.