(Android) 패키지명으로 SHA-1 키값 가져오는 방법

StringBuilder sha1 = new StringBuilder();
try {
    PackageInfo packageInfo = getPackageManager().getPackageInfo(getReferrer().getHost(), PackageManager.GET_SIGNATURES);
    Signature[] signatures = packageInfo.signatures;
    Signature signature = signatures[0];
    byte[] cert = signature.toByteArray();
    MessageDigest md = MessageDigest.getInstance("SHA1");
    byte[] publicKey = md.digest(cert);
    for (int i = 0; i < publicKey.length; i++) {
        sha1.append(Integer.toString((publicKey[i] & 0xff) + 0x100, 16).substring(1).toUpperCase());
        if (i < publicKey.length - 1) {
            sha1.append(":");
        }
    }
    // sha1
} catch (Exception e) {
    // on Exception
}