(Tcl) Demonstrate RSA Encrypt/Decrypt using BinData

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Demonstrates how to RSA encrypt and decrypt data contained in a Chilkat BinData object.

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load ./chilkat.dll

# The RSA public key is used for encryption, and the private key for decryption.

# The public key's role is to make encryption accessible to anyone while ensuring that
# only the private key holder can decrypt the messages.
# The public key is designed to be widely distributed so anyone can use it to encrypt messages
# intended for the owner of the private key.

# Load our 2048-bit RSA public key.
set pubKey [new_CkPublicKey]

# In all Chilkat methods expecting a path, you pass either absolute or relative paths.
set success [CkPublicKey_LoadFromFile $pubKey "rsaKeys/myTestRsaPublic.pem"]
if {$success == 0} then {
    puts [CkPublicKey_lastErrorText $pubKey]
    delete_CkPublicKey $pubKey
    exit
}

set rsa [new_CkRsa]

# Tell RSA to use the public key.
CkRsa_ImportPublicKeyObj $rsa $pubKey

# RSA encryption is for small amounts of data, on the order of 200 bytes or less.
# The maximum number of bytes that can be RSA encrypted depends
# on the RSA key size and padding scheme (OAEP padding vs PKCS#1 v1.5 padding).
# For specific limits, see: RSA Encryption Maximum Number of Bytes

# Create some binary data to encrypt.
set bd [new_CkBinData]

set i 0
for {set i 0} {$i <= 49} {incr i} {
    CkBinData_AppendByte $bd $i
}

# Show the bytes to be encrypted in hex format:
puts "To be encrypted: [CkBinData_getEncoded $bd hex]"

# To be encrypted: 000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F202122232425262728292A2B2C2D2E2F3031

# RSA encrypt the contents of the bd, replacing the contents with the RSA encrypted data.
CkRsa_EncryptBd $rsa $bd 0

# Now it is encrypted.
puts "Encrypted size = [CkBinData_get_NumBytes $bd]"
puts [CkBinData_getEncoded $bd hex]

# Encrypted size = 256
# 749ED9D0A8767C06C09AD9697F654F86B145F966722F9714902C4175BDBD02E68984ECF111D4D461
# EDB4A8E677D399D19CCA60F35C6DE9972F4262880FE9D77DB75915393E8E7DB80AAB5E383013FAEB
# 60C77D1E6FECC9A7C8426976416C6218FE7DA998EE063CE709E79C240F8625F4A56A0A33AFD63F7A
# BA26F2A692B42E878C53B78602C725FE63FF961A46A2B9D436E5E3D9D64AE3F1D1F5AD5F5B47FCD69
# 447306B77F2FD6D766CCAA1A110A3371586B43DF0D7FFE2220D1B305CF9371AC342F849FB0C90CD99E
# C176928D877FE1C0DE1A7CB6EB824FEC7E1DCF90EF2C6BA9F1DFD3EBFBE89C51AF074DC6AE02E544A78
# 5018C36D3D48B2EF5202AF61AC

# ------------------------------------------------------------------------------------------------------------------------
# Let's decrypt, which requires the matching private key...

# Load the matching 2048-bit RSA private key.
set privKey [new_CkPrivateKey]

set password "secret"
set success [CkPrivateKey_LoadAnyFormatFile $privKey "rsaKeys/myTestRsaPrivate.pem" $password]
if {$success == 0} then {
    puts [CkPrivateKey_lastErrorText $privKey]
    delete_CkPublicKey $pubKey
    delete_CkRsa $rsa
    delete_CkBinData $bd
    delete_CkPrivateKey $privKey
    exit
}

# Tell the RSA object to use the private key.
CkRsa_ImportPrivateKeyObj $rsa $privKey

# Decrypt
set success [CkRsa_DecryptBd $rsa $bd 1]
if {$success == 0} then {
    puts [CkRsa_lastErrorText $rsa]
    delete_CkPublicKey $pubKey
    delete_CkRsa $rsa
    delete_CkBinData $bd
    delete_CkPrivateKey $privKey
    exit
}

# Examine the contents of bd to see if it now contains the unencrypted original data.
puts "Decrypted: [CkBinData_getEncoded $bd hex]"

# Decrypted: 000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F202122232425262728292A2B2C2D2E2F3031

delete_CkPublicKey $pubKey
delete_CkRsa $rsa
delete_CkBinData $bd
delete_CkPrivateKey $privKey