The engineNextBytes function in classlib/modules/security/src/main/java/common/org/apache/harmony/security/provider/crypto/SHA1PRNG_SecureRandomImpl.java in the SecureRandom implementation in Apache Harmony through 6.0M3, as used in the Java Cryptography Architecture (JCA) in Android before 4.4 and other products, when no seed is provided by the user, uses an incorrect offset value, which makes it easier for attackers to defeat cryptographic protection mechanisms by leveraging the resulting PRNG predictability, as exploited in the wild against Bitcoin wallet applications in August 2013.
