Sea of numbers
The sea of numbers is a printed pattern on tightly closed envelopes that are designed to protect information such as secret numbers from being viewed by unauthorized persons. Regardless of its name, the camouflage pattern can consist not only of densely printed numbers , but also of letters . The sea of numbers is sometimes referred to as the killing grid.
Functional principle and execution
With sufficiently strong light sources , in principle any envelope containing confidential information can be screened. Even with a thorough blackening , the secret sequence of characters is shown with - albeit low - contrast , which can be enhanced with technical aids. A sea of numbers therefore tries less to prevent the screening, but rather it works according to the principle of camouflage : a printed pattern covers the secret information so that the viewer sees the combination of security and secret in the backlight . This camouflage is particularly effective when
- the sea of numbers consists of the same characters or patterns as the secret, i.e. usually letters and digits,
- the printing color of the sea of numbers is clearly darker than that of the secret,
- the arrangement of the characters on the sea of numbers is unsystematic and in particular does not consist of a continuous text against the background of which the secret information could be filtered out (the sequence "abcdefghij" would be unsuitable, for example),
- the degree of coverage of the sea of numbers is sufficiently high, which can be achieved by heavily overlapping characters (an arrangement of characters as in normal printed texts contains too many “ windows ” due to the white areas ).
Use in conjunction with an envelope
Using a sea of numbers only makes sense in connection with a well-sealed envelope . The decisive factor here is not the resistance that the envelope opposes when it is opened, but rather that the authorized person can easily detect the breach of the confidentiality of the letter afterwards . The closure of the envelope must therefore be designed in such a way that it can only be opened through damage that is clearly visible to the layperson .
Due to the fact that the secret information in an envelope is basically easy to access, a sea of numbers can only be used to protect information whose knowledge by third parties is only undesirable but not dangerous, including, for example, bank statements . In the case of secret numbers , misuse must be secured with a “ second key ”, for example with a machine card or, in the case of transaction numbers , with a password .
Individual evidence
- ↑ a b Patent DE20317363U1 from April 1, 2004 on an alternative protection mechanism to the sea of numbers
- ↑ a b ( page no longer available , search in web archives: Patent WO / 2006/002571 ) from January 12, 2006 about an improved version of the sea of numbers
- ↑ Online, Ed .: User Association of German Information Processors and Working Group for Electronic Data Processing and Punch Card Technology, Publishing Company R. Müller, No. 3, 1981
