@import VirgilFoundation;

//...
VSSKeyPair *keyPair = [[VSSKeyPair alloc] initWithPassword:<#Password or nil#>];
NSString *publicKey = [[NSString alloc] initWithData:keyPair.publicKey encoding:NSUTF8StringEncoding];
NSLog(@"%@", publicKey);
NSString *privateKey = [[NSString alloc] initWithData:keyPair.privateKey encoding:NSUTF8StringEncoding];
NSLog(@"%@", privateKey);
//...

//...
// Assuming that we have some initial string message.
NSString *message = @"This is a secret message which should be encrypted.";
// Convert it to the NSData
NSData *toEncrypt = [message dataUsingEncoding:NSUTF8StringEncoding allowLossyConversion:NO];
// Assuming that we have some key pair generated earlier.
// Create a new VSSCryptor instance
VSSCryptor *cryptor = [[VSSCryptor alloc] init];
// Now we should add a key recipient
NSError *error = nil;
if (![cryptor addKeyRecipient:<# Recipient ID #> publicKey:<# keyPair.publicKey #> error:&error]) {
    NSLog(@"Error adding key recipient: %@", [error localizedDescription]);
    return;
}
// And now we can easily encrypt the plain data
NSData *encryptedData = [cryptor encryptData:toEncrypt embedContentInfo:YES error:&error];
if (error != nil) {
    NSLog(@"Error encrypting data: %@", [error localizedDescription]);
    return;
}
//...

//...
// Assuming that we have received some key-based encrypted data.
// Assuming that we have some key pair generated earlier.
// Create a new VSSCryptor instance
VSSCryptor *decryptor = [[VSSCryptor alloc] init];
// Decrypt data
NSError *error = nil;
NSData *plainData = [decryptor decryptData:<# NSData containing encrypted data #> recipientId:<# Recipient ID #> privateKey:<# keyPair.privateKey #> keyPassword:<# Private key password or nil #> error:&error];
if (error != nil) {
    NSLog(@"Error decrypting data: %@", [error localizedDescription]);
    return;
}
// Compose initial message from the plain decrypted data
NSString *initialMessage = [[NSString alloc] initWithData:plainData encoding:NSUTF8StringEncoding];
//...

//...
// Assuming that we have some initial string message.
NSString *message = @"This is a secret message which should be encrypted with password-based encryption.";
// Convert it to the NSData
NSData *toEncrypt = [message dataUsingEncoding:NSUTF8StringEncoding allowLossyConversion:NO];
// Assuming that we have some key pair generated earlier.
// Create a new VSSCryptor instance
VSSCryptor *cryptor = [[VSSCryptor alloc] init];
NSError *error = nil;
if (![cryptor addPasswordRecipient:<# Password to encrypt data with #> error:&error]) {
    NSLog(@"Error adding password recipient: %@", [error localizedDescription]);
    return;
}
// And now we can encrypt the plain data
NSData *encryptedData = [cryptor encryptData:toEncrypt embedContentInfo:YES error:&error];
if (error != nil) {
    NSLog(@"Error encrypting data: %@", [error localizedDescription]);
    return;
}
//...

//...
// Assuming that we have received some password-based encrypted data.
// Assuming that we have some key pair generated earlier.
// Create a new VSSCryptor instance
VSSCryptor *decryptor = [[VSSCryptor alloc] init];
// Decrypt data
NSError *error = nil;
NSData *plainData = [decryptor decryptData:<# NSData with encrypted data #> password:<# Password used for encryption #> error:&error];
if (error != nil) {
    NSLog(@"Error decrypting data: %@", [error localizedDescription]);
    return;
}
// Compose initial message from the plain decrypted data
NSString *initialMessage = [[NSString alloc] initWithData:plainData encoding:NSUTF8StringEncoding];
//...

//...
// Assuming that we have some initial string message that we want to sign.
NSString *message = @"This is a secret message which should be signed.";
// Convert it to the NSData
NSData *toSign = [message dataUsingEncoding:NSUTF8StringEncoding allowLossyConversion:NO];
// Assuming that we have some key pair generated earlier.
// Create a new VSSSigner instance
VSSSigner *signer = [[VSSSigner alloc] init];
// Sign the initial data
NSError *error = nil;
NSData *signature = [signer signData:toSign privateKey:<# keyPair.privateKey #> keyPassword:<# Private key password or nil #> error:&error];
if (error != nil) {
    NSLog(@"Error composing a signature: %@", [error localizedDescription]);
    return;
}
// Use the signature.
//...

//...
// Assuming that we have the public key of a person whose signature we need to verify
// Assuming that we have a NSData object with signed data.
// Assuming that we have a NSData object with a signature.
// Create a new VSSSigner instance
VSSSigner *verifier = [[VSSSigner alloc] init];
// Verify the signature.
NSError *error = nil;
if (![verifier verifySignature:<# NSData containing the signature #> data:<# NSData used to compose the signature #> publicKey:<# keyPair.publicKey #> error:&error]) {
    NSLog(@"Error signature verification: %@", [error localizedDescription]);
    return;
}
// Signature seems OK.
//...

//...
// Assuming that we have some password which the application does not to expose in plain form.
NSString *password = <# NSString: user password in plain form#>;
// Create a new VSSPBKDF instance
// Salt parameter should contain the random sequence of bytes. In general, salt is public information. 
// If salt parameter is nil then VSSPBKDF will generate random salt automatically.
// If it is necessary to generate the same data later based on the user's input of the password
// it is recommended to generate salt data and store it for further use in VSSPBKDF instance creations:
NSData *salt = [VSSPBKDF randomBytesOfSize:<#size_t: size of the salt in bytes or 0 #>];       
// Iterations parameter should contain number of iterations for derivation function.
// If iterations == 0 then VSSPBKDF will use default number of iterations.
VSSPBKDF *pbkdf = [[VSSPBKDF alloc] initWithSalt:<#NSData: salt or nil for default new salt generation#> iterations:<#unsigned int: iterations count or 0 for default count #>];
NSError *error = nil;
// Derive secure sequence of bytes with required size based on the plain password.
NSData *data = [pbkdf keyFromPassword:password size:<# size_t: Desired length in bytes of the output data sequence #> error:&error];
if (error != nil) {
    NSLog(@"Error: %@", [error localizedDescription]);
    return;
} 
// Use the data instead of plain password.
//...