Enumeration in Java5

package enumjava5;

public enum Color {
    RED(255, 0, 0){
        public String getMood(){
            return "live";
        }
    },
    GREEN(0, 255, 0){
        public String getMood(){
            return "rest";
        }  
    
    },
    BLUE(0, 0, 255){
        public String getMood(){
            return "sleep";
        }
    };

    Integer red;
    Integer green;
    Integer blue;

    private Color(Integer red, Integer green, Integer blue){
        this.red = red;
        this.green = green;
        this.blue = blue;
    }

    public String getCode(){
        return red + ", " + green + ", " + blue;
    }

    public abstract String getMood();

    @Override
    public String toString(){
        return "Color #" + this.ordinal() +  ", " +  this.name();
    }
}

• Use keyword enum - public enum Color
• Constuctor is private.
• You can implements yours method: String getCode()
• You can implements yours abstract method: abstract String getMood()
• You can use heritage method: String name(), int ordinal(), <T>[] values(), <T> valueOf(String)

package enumjava5;

public class Main {

   public static void main(String[] args) {

       for (Color color : Color.values()) {

            System.out.println("name: " + color.name() + ", code: " + color.getCode() + ", mood: " + color.getMood() + ", asString: " + color.toString());
       }

    }
}

output:

name: RED, code: 255, 0, 0, mood: live, asString: Color #0, RED
name: GREEN, code: 0, 255, 0, mood: rest, asString: Color #1, GREEN
name: BLUE, code: 0, 0, 255, mood: sleep, asString: Color #2, BLUE

You can use inner enum:

package enumjava5;

public class Outter{
    
  public enum Color{
      RED, GREEN, BLUE;
  }

  public static void main(String[] args){
      for (Color m: Color.values()){
          System.out.println( m.name() );
      }
  }
}

IPv6

IPv6 is not compatible with IPv4.

Address is assign to interface.

Interface has more addresses: e.g. loopback, multicast, local link, global, ...

The length of header is constant. It can use extends header. Extend header have specified order.

Don´t use checksum.

Kinds of address:

unicast

for interface

multicast

for group of computer

anycast

for first computer in group

Don´t use broadcast. In place of broadcast it use multicast.

---

Notation of IPv6 address

IPv4

147.230.49.73

length 32b

4 x 8b

decimal

IPv6

fedc:ba98:7654:3210:fedc:ba98:7654:3210

length 128b

8 x 16b

hexadecimal

---

Shortening IPv6 address

• 0123:0000:0000:0000:fedc:ba98:7654:3210
• 123:0:0:0:fedc:ba98:7654:3210
• 123::fedc:ba98:7654:3210 (allow only one "::" in address)

---

Mapping IPv4 address to IPv6

147.230.49.73

::ffff:93e6:3149 (147=>93, 230=>e6, 49=>31, 73=>49)

::ffff:147.230.49.73

---

Range of IPv6

• ::1/128 loopback
• 2000::/3 Global Unicast
• FC00::/7 Unique Local Unicast
• FE80::/10 Link Local Unicast
• FF00::/8 Multicast

---

Global Unicast

|_ _ _|_|_ _ _ _|

48b - Public NET topology (from provider)

16b - Local SUBNET topology (your net)

64b - Interfaces (your interfaces)

---

Automatic IPv6 configuration

1. Create local link address from MAC address. (fe80::/10 + MAC)
2. Check collision.
3. Waiting for router info about networks or ask about router.
4. Set network parameters.

---

Security

Ipv6 mandatory use IPsec. It offers authentication, encryption, tunnelling.

Spring AOP with annotation

Aspect

Combination of advice and pointcuts.

Advice

The implementation of functionality that will be applied.

Pointcut

A rule for matching the parts of the object model that the functionality will be applied to.

---

Enable annotation

<aop:aspectj-autoproxy />

---

Aspect

package org.xyz;
import org.aspectj.lang.annotation.Aspect;

@Aspect
public class NotVeryUsefulAspect {

}

---

Pointcut

@Pointcut("execution(* transfer(..))")// the pointcut expression
private void anyOldTransfer() {}// the pointcut signature

Combining pointcut expressions

@Pointcut("execution(public * *(..))")
private void anyPublicOperation() {}
    
@Pointcut("within(com.xyz.someapp.trading..*)")
private void inTrading() {}
    
@Pointcut("anyPublicOperation() && inTrading()")
private void tradingOperation() {}

@Aspect
public class BeforeAspect {
                                                            
  @Pointcut("execution(* com.apress.prospring2.ch06.services.*.*(..))")
  private void serviceExecution() { }
  @Pointcut(
      "execution(* com.apress.prospring2.ch06.services.UserService.login(..))")
  private void loginExecution() { }
  @Before("serviceExecution() && !loginExecution()")
  public void beforeLogin() throws Throwable {
      if (SecurityContext.getCurrentUser() == null)
          throw new RuntimeException("Must login to call this method.");
  }
}

Sharing common pointcut definitions

package com.xyz.someapp;

import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;

@Aspect
public class SystemArchitecture {

  /**
   * A join point is in the web layer if the method is defined
   * in a type in the com.xyz.someapp.web package or any sub-package
   * under that.
   */
  @Pointcut("within(com.xyz.someapp.web..*)")
  public void inWebLayer() {}

  /**
   * A join point is in the service layer if the method is defined
   * in a type in the com.xyz.someapp.service package or any sub-package
   * under that.
   */
  @Pointcut("within(com.xyz.someapp.service..*)")
  public void inServiceLayer() {}

  /**
   * A join point is in the data access layer if the method is defined
   * in a type in the com.xyz.someapp.dao package or any sub-package
   * under that.
   */
  @Pointcut("within(com.xyz.someapp.dao..*)")
  public void inDataAccessLayer() {}

  /**
   * A business service is the execution of any method defined on a service
   * interface. This definition assumes that interfaces are placed in the
   * "service" package, and that implementation types are in sub-packages.
   * 
   * If you group service interfaces by functional area (for example, 
   * in packages com.xyz.someapp.abc.service and com.xyz.def.service) then
   * the pointcut expression "execution(* com.xyz.someapp..service.*.*(..))"
   * could be used instead.
   *
   * Alternatively, you can write the expression using the 'bean'
   * PCD, like so "bean(*Service)". (This assumes that you have
   * named your Spring service beans in a consistent fashion.)
   */
  @Pointcut("execution(* com.xyz.someapp.service.*.*(..))")
  public void businessService() {}
  
  /**
   * A data access operation is the execution of any method defined on a 
   * dao interface. This definition assumes that interfaces are placed in the
   * "dao" package, and that implementation types are in sub-packages.
   */
  @Pointcut("execution(* com.xyz.someapp.dao.*.*(..))")
  public void dataAccessOperation() {}

}

Examples of common pointcut expressions

execution(public * *(..))

the execution of any public method

execution(* set*(..))

the execution of any method with a name beginning with "set"

execution(* com.xyz.service.AccountService.*(..))

the execution of any method defined by the AccountService interface

execution(* com.xyz.service.*.*(..))

he execution of any method defined in the service package

execution(* com.xyz.service..*.*(..))

the execution of any method defined in the service package or a sub-package

within(com.xyz.service.*)

any join point (method execution only in Spring AOP) within the service package

within(com.xyz.service.*)

any join point (method execution only in Spring AOP) within the service package

within(com.xyz.service..*)

any join point (method execution only in Spring AOP) within the service package or a sub-package

this(com.xyz.service.AccountService)

any join point (method execution only in Spring AOP) where the proxy implements the AccountService interface

target(com.xyz.service.AccountService)

any join point (method execution only in Spring AOP) where the target object implements the AccountService interface

args(java.io.Serializable)

any join point (method execution only in Spring AOP) which takes a single parameter, and where the argument passed at runtime is Serializable

@target(org.springframework.transaction.annotation.Transactional)

any join point (method execution only in Spring AOP) where the target object has an @Transactional annotation

@annotation(org.springframework.transaction.annotation.Transactional)

any join point (method execution only in Spring AOP) where the executing method has an @Transactional annotation

@args(com.xyz.security.Classified)

any join point (method execution only in Spring AOP) which takes a single parameter, and where the runtime type of the argument passed has the @Classified annotation

bean(tradeService

any join point (method execution only in Spring AOP) on a Spring bean named 'tradeService'

bean(*Service)

any join point (method execution only in Spring AOP) on Spring beans having names that match the wildcard expression '*Service'

---

Advice

As parameter of advice method you can use org.aspectj.lang.JoinPoint. Class which implements this interface have method: getTarget(), getArgs(), getSignature(), getThis(). You can use this method in advice. For example see @After advice.

Advice with reference to pointcut

import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;

@Aspect
public class BeforeExample {

  @Before("com.xyz.myapp.SystemArchitecture.dataAccessOperation()")
  public void doAccessCheck() {
    // ...
  }

}

Advice with in-place pointcut

import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;

@Aspect
public class BeforeExample {

  @Before("execution(* com.xyz.myapp.dao.*.*(..))")
  public void doAccessCheck() {
    // ...
  }

}

After returning advice

import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.AfterReturning;

@Aspect
public class AfterReturningExample {

  @AfterReturning(
    pointcut="com.xyz.myapp.SystemArchitecture.dataAccessOperation()",
    returning="retVal")
  public void doAccessCheck(Object retVal) {
    // ...
  }
  
}

After throwing advice

import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.AfterThrowing;

@Aspect
public class AfterThrowingExample {

  @AfterThrowing(
    pointcut="com.xyz.myapp.SystemArchitecture.dataAccessOperation()",
    throwing="ex")
  public void doRecoveryActions(DataAccessException ex) {
    // ...
  }

}

After (finally) advice

import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.After;

@Aspect
public class AfterFinallyExample {

  @After("com.xyz.myapp.SystemArchitecture.dataAccessOperation()")
  public void doReleaseLock( JoinPoint jp ) {
    // ...
    Object[] targetMethodArgs = jp.getArgs();
    //...
  }

}

Around advice

import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.ProceedingJoinPoint;

@Aspect
public class AroundExample {

  @Around("com.xyz.myapp.SystemArchitecture.businessService()")
  public Object doBasicProfiling(ProceedingJoinPoint pjp) throws Throwable {
    // start stopwatch
    Object retVal = pjp.proceed();
    // stop stopwatch
    return retVal;
  }

}

Passing parameters to advice

@Before("com.xyz.myapp.SystemArchitecture.dataAccessOperation() &&" + 
        "args(account,..)")
public void validateAccount(Account account) {
  // ...
}

@Pointcut("com.xyz.myapp.SystemArchitecture.dataAccessOperation() &&" + 
          "args(account,..)")
private void accountDataAccessOperation(Account account) {}

@Before("accountDataAccessOperation(account)")
public void validateAccount(Account account) {
  // ...
}

@Before(
   value="com.xyz.lib.Pointcuts.anyPublicMethod() && target(bean) && @annotation(auditable)",
   argNames="bean,auditable")
public void audit(JoinPoint jp, Object bean, Auditable auditable) {
  AuditCode code = auditable.value();
  // ... use code, bean, and jp
}

---

Exception handling in Spring MVC

SimpleMappingExceptionResolver

---

Specific Exception handler

Class SimpleleMappingExceptionResolver implements interface HandlerExceptionResolver. You can implement own specific class or extends class SimpleleMappingExceptionResolver.

---

MailErrorHandlerException

If occure some exception it send mail.

public class ErrorHandlerController implements HandlerExceptionResolver{

    public static final String DEFAULT_EXCEPTION_ATTRIBUTE = "exception";
    public static final String DEFAULT_ERROR_WIEW = "error";
   
    private MailManager mailManager;
    private String from;
    private String to;
    private String subject;
    private String defaultErrorView = DEFAULT_ERROR_WIEW;
    private String exceptionAttribute = DEFAULT_EXCEPTION_ATTRIBUTE;

    @Override
    public ModelAndView resolveException(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) {

        if (mailManager != null && from != null && to != null && subject != null){
            sendMailToWebmaster(ex);
        }

        return getModelAndView(defaultErrorView, ex);
    }

    private void sendMailToWebmaster(Exception ex) {
        mailManager.setFrom(  from );
        mailManager.setTo( to );
        mailManager.setSubject( subject );
        mailManager.setText( stack2string( ex ));
        mailManager.sendMail();
    }

    protected ModelAndView getModelAndView(String viewName, Exception ex) {
         ModelAndView mv = new ModelAndView(viewName);       
         mv.addObject(this.exceptionAttribute, ex);      
         return mv;
    }

    public static String stack2string(Exception e) {
            StringWriter sw = new StringWriter();
            PrintWriter pw = new PrintWriter(sw);
            e.printStackTrace(pw);
            return "------\r\n" + sw.toString() + "------\r\n";
    }
    
    public void setDefaultErrorView(String defaultErrorView) {
        this.defaultErrorView = defaultErrorView;
    }

    public void setExceptionAttribute(String exceptionAttribute) {
        this.exceptionAttribute = exceptionAttribute;
    }

    public void setMailManager(MailManager mailManager) {
        this.mailManager = mailManager;
    }

    public void setFrom(String from) {
        this.from = from;
    }

    public void setSubject(String subject) {
        this.subject = subject;
    }

    public void setTo(String to) {
        this.to = to;
    }
}

Exception handling

Exception - special conditions that change the normal flow of program execution.

---

Exception hierarchy

Your exception extend Exception.

---

Type of exception

• Checked exception
• Unchecked exception

---

Standart checked exception

• IllegalArgumentException
• IllegalStateException
• NullPointerException
• IndexOutOfBoundsException
• ConcurentModificationException
• UnsupportedOperationException
• AritmeticException
• NumberFormatException

---

Exception handle

try{
    //protected block
}catch(Datovy typ výjimky){
    //exception handling
}finally{
    //this code it execute every time
} 

Block finally it will execute always.

---

Exception chaining

public void configure() throws ConfigurationException{
    try{
        ...
        ...
    }catch(FileNotFoundException e){
        throw new ConfigurationException("Config file not exists.",e);
    }catch(PropertyMissingException e){
        throw new ConfigurationException("Missing argument.",e);
    }catch(InvalidFormatException e){
        throw new ConfigurationException("Unknown argument",e);
    }
} 

---

Exception mesage

public IndexOutOfBoundException( int lowerBound, int upperBound, int index){      
    super ("Lower bound:" +  lowerBound +
                ", Upper bound: " + upperBound +
                ", Index: " + index);              
    )
}

---

Tag checkboxes in Spring MVC

In jsp page with Spring MVC you can use form tags.

With tag checkboxes you can create elegant structure of code in form, for example if you have typical 1:N or M:N relation between model classes.

I show 1:N relation between SECTION and PRODUCT class. It example uses Spring MVC and form-tag checkboxes.

---

Class Section

Section class is common POJO. Class contains reference to Product class.

public class Section {
    ...
    private List products;
    ...        
}

Class Product

Correct designed method boolean equals:Obj is very important for useful usage checkboxes tag.

public class Product {
    
    private Integer Id;
    private String title;
    
    ...

    @Override
    public boolean equals(Object obj) {
        if (obj == null) {
            return false;
        }
        if (getClass() != obj.getClass()) {
            return false;
        }
        final Product other = (Product) obj;
        if (this.Id != other.Id && (this.Id == null || !this.Id.equals(other.Id))) {
            return false;
        }
        if ((this.title == null) ? (other.title != null) : !this.title.equals(other.title)) {
            return false;
        }
        return true;
    }
}

Controller

It is important create Property editor for reference class (Product). Property editor is register in method initBinder. As you see the attribute allProducts in method getAllProducts is automatically putting to model. It is need in view section_edit.jsp.

@ModelAttribute("allProducts")
public List getAllProducts(){
     return productDao.all();
}

@RequestMapping(value="/section_edit.htm", method=RequestMethod.GET)   
public Section sectionEdit(Integer sectionId){
     return sectionDao.findById(sectionId);
}

@RequestMapping(value="/section_edit.htm", method=RequestMethod.POST)   
public String sectionEdit(Section section, Errors errors){               
     ...
     sectionDao.saveOrUpdate(section);
     return "redirect:/sections.htm";
}

@InitBinder
public void initBinder(WebDataBinder binder) {       
   binder.registerCustomEditor(Product.class, new ProductPropertyEditor());     
}

ProductPropertyEditor

In ProductProperty editor I override only method void setAsText:String. This method create Product instance from product.id represented as test in jsp form (section_edit.jsp).

public class ProductPropertyEditor extends PropertyEditorSupport{
    ...        
    @Override
    public void setAsText(final String text) {
        setValue(productDao.findById(Integer.parseInt(text)));
    }
    
}

section_edit.jsp

Expression ${allProducts} read model attribute allProduct setting in controller. It contain List of all products. As value of checkboxes tag attribute itemValue I set id. It use product.id value and this value can read method void setAsText:String from ProductPropertyEditor, when user submit form.

When tag checkboxes iterate items allProducts, then every Product from allProducts List is compare with Product from Section.products List. When they are the same, then will be rendered checkbox with checked attribute.

Checkbox will bee checked when Product from List of Section.products equals Product from List of allProduct.

You must override toString method in reference object (Product). It is very important behaviour of checkboxes tag from Spring checkboxes tag documentation.

---

Conclusion

Checkbox is checked when:

• Property is Collection or array and contains the same Object as wrapped Collection.

GnuPG

GnuPG ( GNU Privacy Guard ) is the GNU project's complete and free implementation of the OpenPGP standard. GnuPG allows to encrypt and sign your data and communication.

PGP use asymmetrics cryptography. It mean, that PGP use two keys.

• private key
• public key

Public key use to verification sign of private key. With public key you can also encrypt text. Decryption is possibly only with private key.
After generate your keys you must protect your private key and import your public key to Key server in Internet. Key server is repository of public PGP keys. You can search and take public keys of other people there.
If you want use GnuPG in comfortable way, you use Firefox plug-in FireGPG.

---

Create keys

$ gpg --gen-key

gpg (GnuPG) 1.4.9; Copyright (C) 2008 Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Please select what kind of key you want:
(1) DSA and Elgamal (default)
(2) DSA (sign only)
(5) RSA (sign only)
Your selection? 1
DSA keypair will have 1024 bits.
ELG-E keys may be between 1024 and 4096 bits long.
What keysize do you want? (2048) 2048
Requested keysize is 2048 bits
Please specify how long the key should be valid.
0 = key does not expire
  = key expires in n days
w = key expires in n weeks
m = key expires in n months
y = key expires in n years
Key is valid for? (0) 2y
Key expires at Tue 20 Dec 2011 07:02:09 PM CET
Is this correct? (y/N) y

You need a user ID to identify your key; the software constructs the user ID
from the Real Name, Comment and Email Address in this form:
"Heinrich Heine (Der Dichter) "

Real name: Tomas Jurman
Email address: your@email.com
Comment:
You selected this USER-ID:
"Tomas Jurman "

Change (N)ame, (C)omment, (E)mail or (O)kay/(Q)uit? O
You need a Passphrase to protect your secret key.

We need to generate a lot of random bytes. It is a good idea to perform
some other action (type on the keyboard, move the mouse, utilize the
disks) during the prime generation; this gives the random number
generator a better chance to gain enough entropy.
.+++++++++++++++.++++++++++.+++++.++++++++++++++++++++.+++++..+++++++++++++++++++++++++.++++++++++.+++++++++++++++.+++++++++++++++.++++++++++>++++++++++.........+++++
We need to generate a lot of random bytes. It is a good idea to perform
some other action (type on the keyboard, move the mouse, utilize the
disks) during the prime generation; this gives the random number
generator a better chance to gain enough entropy.
+++++..+++++.++++++++++.++++++++++++++++++++.++++++++++.+++++..++++++++++..+++++.+++++...+++++.++++++++++++++++++++++++++++++++++++++++.+++++.+++++....+++++++++++++++>.++++++++++>...+++++...>+++++........................................................................................................................+++++^^^^^^^^^^^
gpg: key 1DA0400B marked as ultimately trusted
public and secret key created and signed.

gpg: checking the trustdb
gpg: 3 marginal(s) needed, 1 complete(s) needed, PGP trust model
gpg: depth: 0  valid:   2  signed:   0  trust: 0-, 0q, 0n, 0m, 0f, 2u
gpg: next trustdb check due at 2011-12-19
pub   1024D/1DA0400B 2009-12-20 [expires: 2011-12-20]
Key fingerprint = 30DA B2F5 67B6 52D5 CEFE  B8F3 3500 2542 1DA0 400B
uid                  Tomas Jurman 
sub   2048g/8273984F 2009-12-20 [expires: 2011-12-20]

List keys

$ gpg --list-keys

pub   1024D/09CEB475 2009-12-19 [expires: 2011-12-19]
uid                  Tomáš Jurman 
sub   2048g/4288E83B 2009-12-19 [expires: 2011-12-19]

You can see your ID (hexadecimal number after slash - 09CEB475), identity (name and email address), expiration time and other.

Create revocation key

If You want to revoke your keys for reason If has been your keys compromised. (your private key become public known), you must prepare revocation keys.

It is good idea, prepare your revocation keys immediately after generate your keys. Because if you for example by mistake delete your private key, you can not generate your revocation keys. You can prepare revocation keys in advance, save revocation key to file and use in future if it you need.
$ gpg --gen-revoke 4CA09BBE

sec  1024D/4CA09BBE 2009-12-20 tomas jurman 

Create a revocation certificate for this key? (y/N) y
Please select the reason for the revocation:
0 = No reason specified
1 = Key has been compromised
2 = Key is superseded
3 = Key is no longer used
Q = Cancel
(Probably you want to select 1 here)
Your decision? 1
Enter an optional description; end it with an empty line:
> Key has been compromised
> My women bought my private notebook with my private keys.
>
Reason for revocation: Key has been compromised
Key has been compromised
My women bought my private notebook with my private keys.
Is this okay? (y/N) y

You need a passphrase to unlock the secret key for
user: "tomas jurman "
1024-bit DSA key, ID 4CA09BBE, created 2009-12-20

ASCII armored output forced.
Revocation certificate created.

Please move it to a medium which you can hide away; if Mallory gets
access to this certificate he can use it to make your key unusable.
It is smart to print this certificate and store it away, just in case
your media become unreadable.  But have some caution:  The print system of
your machine might store the data and make it available to others!
-----BEGIN PGP PUBLIC KEY BLOCK-----
Version: GnuPG v1.4.9 (GNU/Linux)
Comment: A revocation certificate should follow

iJsEIBECAFsFAksufFxUHQJLZXkgaGFzIGJlZW4gY29tcHJvbWlzZWQKTXkgd29t
ZW4gYm91Z2h0IG15IHByaXZhdGUgbm90ZWJvb2sgd2l0aCBteSBwcml2YXRlIGtl
eXMuAAoJEK4w30tMoJu+5GEAoJ7gDvekN3DHDj/fg97N6Wx3aM1yAKCrW/EBaVnf
A0AzEx5BoJ01raygyg==
=5ln0
-----END PGP PUBLIC KEY BLOCK-----

Last part of statement you copy and paste to file with name for example "revok.key" and retain in secret place.

Revocation keys

$ gpg --import revok.key

Delete keys

$ gpg --delete-secret-keys 1DA0400B
$ gpg --delete-keys 1DA0400B
First you must delete private key and then public key.

Import your public key to Key server

For sending your public key to Key server you must determine your key ID.
$ gpg --send-keys 09CEB475

gpg: sending key 09CEB475 to hkp server keys.gnupg.net

Search public keys in Key server

$ gpg --search-key yourFriend@email.com

gpg: searching for "yourFriend@email.com" from hkp server keys.gnupg.net
(1) Tomáš Jurman 
1024 bit DSA key 05CEA475, created: 2009-12-19
Keys 1-1 of 1 for "yourFriend@email.com".  Enter number(s), N)ext, or Q)uit > 1
gpg: requesting key 05CEA475 from hkp server keys.gnupg.net
gpgkeys: key 05CEA475 not found on keyserver
gpg: no valid OpenPGP data found.
gpg: Total number processed: 0

The key will bee find and GPG offer you to import key in your keys store.

Export public key to file

$ gpg -a --export your@email.com > my.key

Export secret key to file

gpg --export-secret-keys -a [id] > /home/tomas/mySecrKey.txt
Value Id is optional. If you dont use id, gpg export all yours secret keys

Import public key from file

$ gpg --import my.key

Encrypt file

$ gpg -ear 09CEB475 sourcerPlainText.txt
-e = encryt, -r = recipient, -o = output, -a = armor (to ascii)

Decrypt file

$ gpg -d encryptOutputFile.txt

Encrypt and Sign

gpg -esr 09CEB475 -u 16582121 sourcerPlainText.txt
This create .pgp file decript of recipient with ID 09CEB475 and sign of user with ID 16582121
-e = encrypt; -s - sign; -r = recipient; -u = user

Sign

• $ gpg -s sourcerPlainText.txt
  Create .pgp file. Use compression and Contain source file data.
• gpg --clearsign sourcerPlainText.txt
  Create .asc file. Dont use compression. Contain source file data.
• gpg -b sourcerPlainText.txt
  Create .asc file. Create only sign, not contains data from file.

optional: -a = armor (to ascii); -u = user
gpg -bau 16582121 sourcerPlainText.txt

Fingerprint

gpg --fingerprint [ID | email]

Verify sign

You need 2 files. First file is Sign and second file contains some data for verify.
gpg --verify test.txt.sig test.txt

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Create encrypt and sign file for SIMS

Every quarter of year we have to send encrypt and sign file to SIMS.
As -r (recipient) use ID or email address of Matrika studentu - sber dat
As -u (user) use your ID or your email address.
Don´t forget use switch --pgp6.

1. gpg -easr sims@ics.muni.cz -u yourSchool@emailAddress.cz --pgp6 -o sims.pgp sims.xml
2. gpg -easr 8E4E1C1C -u 16582121 --pgp6 -o sims.pgp sims.xml

-e = encrypt; -s - sign; -r = recipient; -u = user; -o = output, -a = armor (to ascii)