METHOD FOR ENCRYPTING AND DECRYPTING DATA WITH A ONE-TIME-KEY

Abstract

A method for encrypting and decrypting data with a session key is proposed. The data is exchanged between a first data processing device and a second data processing device via a communications link that is equipped with a communications server. The method exhibits process steps concerning the generation of a permanent common start value and the provision of a formation rule for the session key, process steps concerning the generation of a session key for the encryption of the data, process steps concerning the encryption of data of the first data processing device using the session key, process steps concerning the generation of a session key for decryption of the data and process steps concerning the decryption of the data.

Claims

1. Method for encrypting and decrypting data which is exchanged between a first data processing device and a second data processing device via a communications link, with a session key, wherein the first data processing device is connected to the second data processing device via the communications link and the communications link exhibits a communications server, comprising the following process steps concerning the generation of a permanent common start value and the provision of a formation rule for the session key: Generation of a start value in the first data processing device, Saving of the start value in a memory of the first data processing device, Exchanging of this start value between the first and second data processing device, Provision of a formation rule in the communications server which generates a session key from at least the start value and a random value generated in the communications server, and the following process steps concerning the generation of a session key for the encryption of the data: Generation of a random value in the communications server, Saving of the random value in the communications server, Either output of the start value by the first data processing device to the communications server and generation of a session key from the start value and the random value by the communications server using the formation rule Or output of the random value and the formation rule by the communications server to the first data processing device and generation of a session key from the start value and the random value by the first data processing device using the formation rule, and the following process steps concerning the encryption of data of the first data processing device using the session key: Encryption of the data using the session key on the communications server or encryption of the data using the session key in the first data processing device and Output of the encrypted data to the communications server, Saving of the encrypted data on the communications server, Deletion of the session key, and the following process steps concerning the generation of a session key for the decryption of the data: Either output of the start value from the second data processing device to the communications server and generation of the session key from the start value and the random value saved on the communications server by the communications server using the formation rule Or output of the random value and the formation rule from the communications server to the second data processing device and generation of the session key from the start value and the random value by the second data processing device using the formation rule, and the following process steps concerning the decryption of the data Either decryption of the encrypted data with the session key by the communications server and output of the decrypted data to the second data processing device Or output of the encrypted data to the second data processing device and decryption of the data in the second data processing device using the session key, Deletion of the session key and the random value.

2. Method according to claim 1, wherein a start value key for encrypting the start value is generated, that the start value is encrypted by the first data processing device using the start value key before it is output to the second data processing device, that the start value key is input into the second data processing device along a channel of communication other than the communications link, and that the encrypted start value in the second data processing device is decrypted using the start value key.

3. Method according to claim 1, wherein the start value is formed according to a random principle.

4. Method according to claim 1, wherein first a session key is formed on the communications server using the formation rule, before the unencrypted data is output from the first data processing device to the communications server.

5. Method according to claim 1, wherein the data exchange takes place over a communications link designed as a secure channel of communication between the first data processing device and the communications server, and between the communications server and the second data processing device.

6. Method according to claim 1, wherein the first data processing device outputs a message to the second data processing device if data of the first data processing device that is intended for the second data processing device is encrypted with a session key and saved on the communications server.

7. Method according to claim 1, wherein the communications server outputs a message to the second data processing device if data of the first data processing device that is intended for the second data processing device is saved encrypted on the communications server.

8. Method according to claim 1, wherein the start value in a memory of the first data processing device and in a memory of the second data processing device is permanently saved and remains constant for several communication processes.

9. Method according to claim 1, wherein the formation rule is a key derivation function.

Description

Drawing

[0170] The drawing shows various model embodiments of the method according to the invention.

[0171] FIG. 1 Generation of a session key,

[0172] FIG. 2 Encryption of data,

[0173] FIG. 3 Decryption of data,

[0174] FIG. 4 First model embodiment of the method,

[0175] FIG. 5 Second model embodiment of the method,

[0176] FIG. 6 Third model embodiment of the method,

[0177] FIG. 7 Fourth model embodiment of the method,

[0178] FIG. 8 Fifth model embodiment of the method,

[0179] FIG. 9 Sixth model embodiment of the method,

[0180] FIG. 10 Seventh model embodiment of the method,

[0181] FIG. 11 Eighth model embodiment of the method,

[0182] FIG. 12 Ninth model embodiment of the method,

[0183] FIG. 13 Tenth model embodiment of the method,

[0184] FIG. 14 Eleventh model embodiment of the method,

[0185] FIG. 15 Twelfth model embodiment of the method,

[0186] FIG. 16 Thirteenth model embodiment of the method,

[0187] FIG. 17 Fourteenth model embodiment of the method,

[0188] FIG. 18 Fifteenth model embodiment of the method,

[0189] FIG. 19 Sixteenth model embodiment of the method.

DESCRIPTION OF THE MODEL EMBODIMENTS

[0190] FIG. 1 shows the generation of a session key from a start value and a random value using a formation rule. The start value is symbolised by a star. The random value is represented by two arrows crossing over. The session key is symbolised by a key. Generation of the session key is symbolised by a key from which lines radiate outwards. The start value is saved in a first data processing device and in a second data processing device. These are not represented in FIG. 1. The random value is generated in a communications server. The communications server is not represented in FIG. 1. It is part of a communications link over which the first and the second data processing device are connected to each other. The formation rule is saved in the communications server. The symbol for the session key is also contained in FIGS. 2 and 3. The symbol for the generation of the session key is contained in FIGS. 4 to 19.

[0191] FIG. 2 shows the encryption of data. The unencrypted data is symbolised by a stack of paper. The encrypted data is symbolised by a stack of paper with a padlock. The encryption of the data is symbolised by a padlock inside a circle with arrows pointing in the clockwise direction. These symbols for the unencrypted and encrypted data and for the encryption of data are also contained in FIGS. 3 to 19.

[0192] FIG. 3 shows the decryption of data. Here, the decryption of data is symbolised by a padlock inside a circle with arrows pointing in the anticlockwise direction.

[0193] FIGS. 4 to 19 show sixteen model embodiments of the method for the encryption and decryption of data.

[0194] The following table contains a list of the aforementioned sixteen model embodiments. They differ in respect of the devices in which the generation of the session key and the encryption and decryption of the data takes place. The devices here are the communications server, the first data processing device and the second data processing device. The table and FIGS. 4 to 19 show: [0195] the abbreviation server for the communications server, [0196] the abbreviation DV1 for the first data processing device, and [0197] the abbreviation DV2 for the second data processing device.

[0198] For the individual lines in the table, the X indicates where the generation of the session key and the encryption and decryption of the data takes place. The number in the first column indicates the number of the model embodiment.

TABLE-US-00001 Generation Generation of the session Encryption of the session Decryption key for of the key for of the encryption data decryption data Variant Server DV1 Server DV1 Server DV2 Server DV2 1 X X X X 2 X X X X 3 X X X X 4 X X X X 5 X X X X 6 X X X X 7 X X X X 8 X X X X 9 X X X X 10 X X X X 11 X X X X 12 X X X X 13 X X X X 14 X X X X 15 X X X X 16 X X X X

[0199] The symbols for the generation of the session key, the encryption of the data and the decryption of the data are represented in FIGS. 4 to 19 in each case next to the device in which the process in question takes place. The arrows between the first data processing device and the communications server as well as between the communications server and the second data processing device symbolise output of the data. If the symbol for the unencrypted data is shown at this arrow, the data is output unencrypted. If the symbol for the encrypted data is shown in this arrow, the data is output encrypted. The output of start value, random value, formation rule or session key is not represented in FIGS. 4 to 19 for the sake of greater clarity. The following applies for all FIGS. 4 to 19:

[0200] 1. If the session key for the encryption of the data is formed by the communications server, the start value from the first data processing device to the communications server is output, which then forms the session key, from the random value it forms and the start value, using the formation rule.

[0201] 2. If the session key for the decryption of the data is formed by the communications server, the start value from the second data processing device to the communications server is output, which then forms the session key, from the random value it saves and the start value, using the formation rule.

[0202] 3. If the session key for the encryption of the data is formed by the first data processing device, the random value formed by the communications server and the formation rule are output from the communications server to the first data processing device. These form the session key from their start value and the random value, using the formation rule.

[0203] 4. If the session key for the decryption of the data is formed by the second data processing device, the random value saved by the communications server and the formation rule are output from the communications server to the second data processing device. These form the session key from their start value and the random value, using the formation rule.

[0204] 5. If the key for the encryption of the data is generated by the communications server and if encryption also takes place there, the session key for the encryption of the data need not be output to the first data processing device. The same applies to the session key for the decryption of the data and the second data processing device if the generation of the session key for the decryption of the data and decryption is performed by the communications server.

[0205] 6. If the key for the encryption of the data is generated by the first data processing device and if encryption also takes place there, the session key for the encryption of the data need not be output to the communications server. The same applies to the decryption of the data by the second data processing device if the session key is formed and the data decrypted there.

[0206] 7. If the key for the encryption of the data is generated by the communications server and if the encryption of the data takes place in the first data processing device, the session key must be output from the communications server to the first data processing device.

[0207] 8. If the key for the encryption of the data is generated by the first data processing device and if the encryption of the data takes place in the communications server, the session key must be output from the first data processing device to the communications server.

[0208] 9. If the key for the decryption of the data is generated by the communications server and if the decryption of the data takes place in the second data processing device, the session key must be output from the communications server to the second data processing device.

[0209] 10. If the key for the decryption of the data is generated by the second data processing device and if the decryption of the data takes place in the communications server, the session key must be output from the second data processing device to the communications server.

[0210] FIG. 4 shows a first model embodiment. In this, the data is output unencrypted from the first data processing device to the communications server. In addition, the start value is output from the first data processing device to the communications server. The latter forms a session key from the start value of the first data processing device and the random value formed by it, encrypts the data with this session key and saves the encrypted data. To decrypt the data, the second data processing device outputs its start value to the communications server. The latter forms a session key from the random value that is still saved and the start value of the second data processing device and decrypts the data before this unencrypted data is output to the second data processing device.

[0211] The second model embodiment according to FIG. 5 differs from the first model embodiment in that the decryption of the data takes place in the second data processing device. Here, the session key formed in the communications server for decrypting the data is output to the second data processing device. The data is output encrypted from the communications server to the second data processing device and decrypted there with the session key.

[0212] The third model embodiment according to FIG. 6 differs from the first model embodiment in that the generation of the session key for the decryption of the data takes place in the second data processing device. Here, the formation rule and the random value are output from the communications server to the second data processing device. The session key for decrypting the data is then output from the second data processing device to the communications server, which decrypts the data with this session key.

[0213] The fourth model embodiment according to FIG. 7 differs from the first model embodiment according to FIG. 4 in that the second data processing device generates the session key and that the second data processing device decrypts the data.

[0214] The fifth model embodiment according to FIG. 8 differs from the first model embodiment according to FIG. 4 in that the encryption of the data takes place in the first data processing device.

[0215] The sixth model embodiment according to FIG. 9 corresponds to the second model embodiment according to FIG. 5, with the difference that the encryption of the data takes place in the first data processing device.

[0216] The seventh model embodiment according to FIG. 10 corresponds to the third model embodiment according to FIG. 6, with the difference that the encryption of the data takes place in the first data processing device.

[0217] The eighth model embodiment according to FIG. 11 corresponds to the fourth model embodiment according to FIG. 6, with the difference that the encryption of the data takes place in the first data processing device.

[0218] The ninth model embodiment according to FIG. 12 differs from the first model embodiment according to FIG. 4 in that the generation of the session key for the encryption of the data takes place in the first data processing device.

[0219] The tenth model embodiment according to FIG. 13 differs from the second model embodiment according to FIG. 5 in that the generation of the session key for the encryption of the data takes place in the first data processing device.

[0220] The eleventh model embodiment according to FIG. 14 differs from the third model embodiment according to FIG. 6 in that the generation of the session key for the encryption of the data takes place in the first data processing device.

[0221] The twelfth model embodiment according to FIG. 15 differs from the fourth model embodiment according to FIG. 7 in that the generation of the session key for the encryption of the data takes place in the first data processing device.

[0222] The thirteenth model embodiment according to FIG. 16 differs from the fifth model embodiment according to FIG. 8 in that the generation of the session key for the encryption of the data takes place in the first data processing device.

[0223] The fourteenth model embodiment according to FIG. 17 differs from the sixth model embodiment according to FIG. 9 in that the generation of the session key for the encryption of the data takes place in the first data processing device.

[0224] The fifteenth model embodiment according to FIG. 18 differs from the seventh model embodiment according to FIG. 10 in that the generation of the session key for the encryption of the data takes place in the first data processing device.

[0225] The sixteenth model embodiment according to FIG. 19 differs from the eighth model embodiment according to FIG. 11 in that the generation of the session key for the encryption of the data takes place in the first data processing device.

[0226] All features of the invention can be material to the invention both individually and in any combination.