A SHORT INTRODUCTION TO CRYPTOGRAPHY AND CERTIFICATES  
In this chapter technical terms become: the Digest (Hash, finger mark), asymmetrical 
Coding (with public/private key), certificates and others, for those 
Importantly are briefly described to work with the product T2U. 
Hash 
Digest or Hash one calls a clear check total of a file or 
a data record. Hashing is the check total from the communicationses (Crc-16, (carriage return character) CCITT, 
Crc-32) in certain view similarly. With the check total one counts from everyone 
Data record or the file a value (typically 16 or 32 bits value), which one with that 
transferred data also passes on. The receiver can again calculate the check total  
in order to examine whether no transfer error arose. With the hash algorithms goes 
one of the fact out that someone "on the line" intentionally the transferred information 
to falsify and hush up could. The result of a hash algorithm is therefore 
typically longer than of a check total algorithm. The most well-known 
Algorithms are MD5, SHA1 some old algorithms MD2, MD4 and the newest, still 
less spread Sha-256, Sha-384, Sha-512. They are listed in the table. 
Algorithm result in bits result in bytes 
MD2 128 16 
MD4 128 16 
T2U documentation 5 OK ONE soft R GmbH 
MD5 128 16 
SHA1 160 20 
Sha-256 256 32 
Sha-384 384 48 
Sha-512 512 64 
Coding 
Coding one calls the unrecognizable making of information, so that only 
authorized readers these to decode can. There is many different coding algorithms 
admits. Some of it are standardized. The most important standardized 
Coding algorithms are implemented under Windows operating systems and 
are available under CryptoAPI. 
For the coding of data a key is used. Only the knowledge of the 
Coding algorithm is sufficient not in order to decode the data. 
Completely in the opposite, those publicly well-known coding algorithms are best 
examined and are considered as the safest. For the decoding of coded data needs 
one a further key. This key is either the same key, which one 
during the coding, in this case speaks one used of one 
symmetrical coding algorithm, or is another key, then 
one speaks of an asymmetrical coding algorithm. 
One calls the key, which is used with symmetrical coding algorithms, 
secret key (key or session key secret). 
With the asymmetrical coding algorithms one needs a pair key: 
one for coding and another for decoding. Most that 
asymmetrical coding algorithms have an important characteristic. Everyone 
Key of a pair of keys is equal: if one with a key 
coded, one needs another for decoding. Two are so seen 
Key two halves of a whole one. With the application of the asymmetrical 
Coding algorithms code a person data and another or even 
several different decode. One generates thus a pair of keys 
(pair of cryptography keys) and one keeps one of the two keys with itself and that 
others one gives to the persons, who may read the coded data. From this 
Note: 
The program T2U calculates Hash values with the help of one 
cryptographic Providers, which is a part of the operating system. 
The algorithms Sha-256, Sha-384 and Sha-512 become only since 
Windows server 2003 supports. If one thus a package with the help of 
from T2UAdmin.exe, that marks 2003 servers not only on Windows 
, should one is used rather with the hash algorithms MD5, 
SHA1 remain. We hope that Microsoft with a new service 
Luggage new, modern hash algorithms even for older 
Operating systems will bring. 
The two keys get scenario their name: one calls one the private 
Key (private keys) and the other one the public key (public keys). 
A large advantage from asymmetrical coding algorithms is that one it to 
Authentifizierung to use can. If we a public key of a person 
and we possess coded data got, those with the public key 
are decodable, then the owner of this private key coded these 
data. 
There are to time very many Hash and coding algorithms, both symmetrical and 
also asymmetrical. Important it is to be understood however that in the comparison the hash algorithms 
, the symmetrical coding algorithms are very fast fast and those 
asymmetrical coding algorithms are very slow, but in addition, to 
safest. Therefore one tries all three groups of algorithms in practice 
to combine to achieve over the desired kind of safety condition and 
to remain in addition still with the acceptable performance. 
If one wants to only authentifizieren for example a file and/or a text, needs 
not to code one the full text. It hands here, a Hashwert, often also as 
Digest or finger mark admits to calculate from the text and this Hash with that 
to code private key. These with the private key coded 
One calls Hash digital signature. If one adds this digital signature to the text, 
then one gets marked data. Everyone, these marked data gets and that 
public key possesses, can the Hashwert from the digital signature decode 
compare and with the again computed Hash. If the Hashwert remained alike, can 
one not only surely its that the text remained unchanged, but one can also 
surely its that it was examined by the owner of a private key. 
Another important example is the asymmetrical coding of data. Those 
asymmetrical coding is substantially slower than the symmetrical. Thus becomes 
the asymmetrical coding so well never for coding data uses. 
Place meal is generated for the data record a symmetrical key 
which can be coded. One often calls this key the session key (session key). The data 
with use of this key and with symmetrical coding algorithms 
are coded. Afterwards the session key with the public key becomes 
from the receiver of these data codes. This coded session key becomes 
together with the coded data stored. Each person, those the private 
Key knows, can first the session key decode and afterwards those 
actual data. This procedure is used, around z. B. To code enamel. 
Similarly the coding of files on a NTFS drive assembly functions. 
If one uses asymmetrical coding algorithms frequently, one becomes with that 
Administrative problem of public keys confronts. Everyone must once 
Pair of keys generate and the public key on to all pass, with those 
one to communicate wants. One must also the public keys of all persons, also 
which one communicates, keep somewhere. Around the whole administration expense too 
facilitates, one certificates suggested. 
A certificate is a digital document, that generally for the safe exchange of 
Information in open networks one uses. Certificates become from one 
Certification body (Certification Authority, APPROX.) digitally marked and know for one 
User, a computer or a service to be issued. 
Usually certificates contain the following information:
· value of the public key of the applicant 
· information for the identification of the applicant, e.g. name and E-Mail address 
· validity period (the period, in which the certificate is valid) 
· information for exhibitor identification 
· the digital signature of the exhibitor, those the validity of the connection between that 
public key and to the identification information of the applicant 
confirms. 
By certificates the number of public keys can dramatically reduced 
become. Everyone needs only the public keys or the certificate of one 
Certification body keep. 

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