Password Encryption up to Oracle 10

Up to and including version 10, Oracle created its encrypted passwords from a concatenation of username and password. I will look at version 11 in future posts:
  

SQL> CREATE USER A IDENTIFIED BY BCDEF
  2  /

User created.

SQL> CREATE USER AB IDENTIFIED BY CDEF
  2  /

User created.

SQL> CREATE USER ABC IDENTIFIED BY DEF
  2  /

User created.

SQL> CREATE USER ABCD IDENTIFIED BY EF
  2  /

User created.

SQL> CREATE USER ABCDE IDENTIFIED BY F
  2  /

User created.

SQL>

The encrypted password was then stored in the PASSWORD column of DBA_USERS:

SQL> SELECT USERNAME, PASSWORD
  2  FROM DBA_USERS
  3  WHERE USERNAME IN ('A','AB','ABC','ABCD','ABCDE')
  4  ORDER BY 1
  5  /

USERNAME                       PASSWORD       
------------------------------ ------------------------------ A                              016811C1486D026B    
AB                             016811C1486D026B    
ABC                            016811C1486D026B                
ABCD                           016811C1486D026B          
ABCDE                          016811C1486D026B

SQL>