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There are two key mechanisms: symmetric and asymmetric key mechanisms. A symmetric key mechanism is not used recently because of difficulty of managing key. The key which is shared between two (or several) parties should be kept as secret. An asymmetric key mechanism is also known as public-private key. A private key is kept as secret by the key owner whereas a public key is known to anyone. Two use cases are considered for this mechanism.

Problem: Bluetooth headphone (LG HBS730 in my case) has been connected but does not displayed in the sound output device list. Environment: Mint Linux 17 Solution: Refer to following links.


Nonce is used to check data is the most recent one. Nonce is a randomly generated number when there is some modification. The figure above (reference: wikipedia) describes an example of usage of nonce in client-server authentication. As seen in the figure, there are two nonces: a server nonce and a client nonce ( = cnonce).

0. Refer to official site ( 1. Prerequisites: refer to requirements section in download page ( 2. correct smime.pod error Error message is like below. installing man1/smime.1 smime.pod around line 272: Expected text after =item, not a number smime.pod around line 276: Expected text after =item, not a number smime.pod around line 280: Expected text after =item, not a number smime.pod around line 285: Expected text after =item, not a number smime.

Find the name of the SD card. (ex> /dev/sdd in my case. You must enter your own SD card device name.) sudo fdisk -l If SD card is already mounted, unmount it. sudo umount [/dev/sdd] Remove partition. sudo fdisk [/dev/sdd] You can delete partition by entering d. (Refer to following info.) m: help. d: delete partition. p: print current partition information. n: make new partition. w: save and exit.

Environment Many-core system with multiple multi-threaded applications. Contribution The paper suggests SBMP (Scalability-Based Manycore Partitioning) scheduler which considers the scalability of each application and allocates the best number of CPU cores in accordance with the scalability. SBMP scheduler outperformed the traditional Linux CPU scheduler (kernel version of about 11%. Problem to solve The system is anticipated to get more number of cores. As the number of cores increases, multiple applications will run on the system simultaneously.

The followings are the three components of the security. Confidentiality To conserve the secrecy of the contents. The contents should not be shown to an unauthorized user. Ex> Encryption Integrity To prevent the contents of data from being modified or deleted by an unauthorized user. Ex> checksum Availability Data should be read or used only by the authorized users with the owner’s intention. In other words, the data should be available to an unauthorized users only when the owner allows it.

Vim tips

divide window [Ctrl] + w v => split vertically. [Ctrl] + w s => split horizontally. :vs filename => split vertically and open file. :sp filename => split horizontally and ope file. :qa close all windows. (in shell) vim -o txt.a txt.b => open txt.a and txt.b in two windows split horizontally. (in shell) vim -O txt.a txt.b => open txt.a and txt.

Problem: Virtualbox does not recognize host’s USBs. Being different from the below screenshot, none of USBs was recognized. Environment: Mint Linux 17, Virtualbox 4.3.10, Virtualbox Guest Additions 4.3.10 (not 4.3.14) [caption id=«attachment_128» align=«aligncenter» width=«854»] After the problem had been fixed, the list of connected USBs were displayed. There was no USB detected before the problem had been solved.[/caption] Solution: Add current user to the vboxusers. Ex> _$ adduser [user name] vboxusers_