Encryption key requirements

The encryption key must meet the following requirements:

• It must be 16 to 21 characters long (21 is recommended).
• It must contain characters from at least three of the following four groups:
• • Uppercase English letters (A–Z)
  • Lowercase English letters (a–z)
  • Westernized Arabic numerals (0–9)
  • Punctuation symbols ` ~ ! @ # $ % ^ & * _ – + = | \ { } [ ] : ; \ " ' < > . ?
• It must not contain a left or right parentheses (that is a "(" or ")" character), a comma (,), or a blank space ( ).