FireEye: The free ones applications Android apps available from the Google Play Store that have over one million downloads have been found to use vulnerable cryptographic systems to protect the sensitive information they store.
An analysis of the most popular free apps (9.339 apps) available in the official Google Store reveals that about 62% of them, or 5.147, were unable to properly secure confidential information, which could allow an attacker to steal the "protected" data by exploiting various weak points.
Her researchers FireEye (you can read more in the official by clicking here) performed the tests on samples that met the popularity criteria mentioned above on November 22, 2014.
Experts looked for vulnerabilities in high entropy, encryption algorithms, and encryption codes.
Most of the products found to be cryptographically insecure were with the encryption algorithms. An attacker could exploit use a reverse dictionary to discover the original string, without knowing the wrenches used for encryption.
The cases of low entropy weaknesses discovered by the security company concerned 1.762 applications that used a static key to encrypt the information that could be extracted to reverse the process.
So beware of what you download, or to be even more confident, of what you store on your devices.
