Ruby

Verify an RSA Signature Against the Signed String

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Demonstrates how to validate an RSA Signature against the string that was signed. Ruby

require 'chilkat'

success = false

# Create the same string we previously signed in this example: 
# RSA Sign utf-8 Bytes of String to get Base64 RSA Signature

sb = Chilkat::CkStringBuilder.new()
crlfLineEnding = true

for i in 0 .. 10
    sb.AppendLine("This is a test.",crlfLineEnding)
end

base64_rsa_sig = "gWgpEXQqvXN6wh0MuFXPiw2xCb8cnmdizBT1TD1Tpm2GlJ8gnD59DGSj35GGXk1tM+mCOvMa2uW/9gmz8p6A90JLbn918i/2wKGvcde4wXnzPO7JADSNn2UwYzf3rp4/q/JrHv1GZETRJhABSFqTxOgdmdbEJQE/zijOSctCtQAM2CTb6t2BO8uHKSSUAwPH2cbeWxqsaVRLT4ruk5nZOxhoLgLMSjupiSzbE8zSTkkFOEHD+Mbb2xwg85AI0E4DsUnp+hLwwtS0blesgSyvtBY8oJODJeFcJsR7JDOTPdzHQHgJRl/2A4ij5xT91TpXy7ok43jhT6O9j7Q3qrafIQ=="

# Get the public key to be used for signature verification.
pubKey = Chilkat::CkPublicKey.new()
success = pubKey.LoadFromFile("rsaKeys/chilkat-rsa-2048.pem")
if (success == false)
    print pubKey.lastErrorText() + "\n";
    exit
end

rsa = Chilkat::CkRsa.new()
success = rsa.UsePublicKey(pubKey)
if (success == false)
    print rsa.lastErrorText() + "\n";
    exit
end

# Verify the string against the signature.
# We signed the utf-8 byte representation of the string, so we must indicate
# to also validate against the utf-8 byte representation.
rsa.put_Charset("utf-8")
rsa.put_EncodingMode("base64")
signedString = sb.getAsString()
success = rsa.VerifyStringENC(signedString,"sha256",base64_rsa_sig)

if (success == false)
    print rsa.lastErrorText() + "\n";
    print "Signature invalid." + "\n";
else
    print "Signature valid." + "\n";
end