diff --git a/host/Crypto/Makefile b/host/Crypto/Makefile
index d635777e..407092b4 100644
--- a/host/Crypto/Makefile
+++ b/host/Crypto/Makefile
@@ -97,6 +97,7 @@ SOURCES += \
 	Noise_NNpsk0_25519_ChaChaPoly_BLAKE2s.cpp \
 	Noise_NNpsk0_25519_ChaChaPoly_SHA256.cpp \
 	Noise_NNpsk0.cpp \
+	NoiseProtobufs.cpp \
 	NoiseProtocolDescriptor.cpp \
 	NoiseSymmetricState_AESGCM_SHA256.cpp \
 	NoiseSymmetricState_ChaChaPoly_BLAKE2s.cpp \
diff --git a/libraries/NoiseProtocol/src/NoiseProtobufs.cpp b/libraries/NoiseProtocol/src/NoiseProtobufs.cpp
new file mode 100644
index 00000000..49c16131
--- /dev/null
+++ b/libraries/NoiseProtocol/src/NoiseProtobufs.cpp
@@ -0,0 +1,679 @@
+/*
+ * Copyright (C) 2018 Southern Storm Software, Pty Ltd.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#include "NoiseProtobufs.h"
+#include <string.h>
+
+/**
+ * \class NoiseProtobufFormatter NoiseProtobufs.h <NoiseProtobufs.h>
+ * \brief Formats data into a buffer using the protobufs format.
+ *
+ * This class provides support for creating messages in the protobufs
+ * format.  Fields in a message consist of a tag followed by a value.
+ *
+ * This implementation provides a subset of the full protobufs encoding,
+ * limited to the types bool, uint32, uint64, sint32, sint64, string,
+ * bytes, and embedded messages.  In addition, tag numbers are limited
+ * to unsigned 8-bit values.
+ *
+ * Reference: https://developers.google.com/protocol-buffers/docs/encoding
+ *
+ * \sa NoiseProtobufParser
+ */
+
+/**
+ * \type NoiseProtobufTag_t
+ * \brief Integer type that defines a protobuf tag number (unsigned 8-bit).
+ */
+
+/**
+ * \brief Constructs a new protobuf formatter.
+ *
+ * \param data Points to the buffer to format fields into.
+ * \param maxSize Maximum size of the buffer in bytes.
+ */
+NoiseProtobufFormatter::NoiseProtobufFormatter(void *data, size_t maxSize)
+    : buf((uint8_t *)data)
+    , maxsz(maxSize)
+    , pos(0)
+    , err(false)
+{
+}
+
+/**
+ * \brief Destroys this protobuf formatter.
+ */
+NoiseProtobufFormatter::~NoiseProtobufFormatter()
+{
+}
+
+/**
+ * \fn size_t NoiseProtobufFormatter::size() const
+ * \brief Returns the final size of the data after all fields have been added.
+ *
+ * \return The number of bytes that were written to the buffer.
+ *
+ * If an error has occurred, then size() will be invalid.
+ *
+ * \sa error()
+ */
+
+/**
+ * \fn bool NoiseProtobufFormatter::error() const
+ * \brief Determine if an error occurred during formatting.
+ *
+ * \return Returns true if the buffer ran out of space while trying to
+ * write the fields; false if formatting was successful.
+ *
+ * \sa size()
+ */
+
+/**
+ * \fn void NoiseProtobufFormatter::addBool(NoiseProtobufTag_t tag, bool value)
+ * \brief Adds a boolean field.
+ *
+ * \param tag Tag number for the field.
+ * \param value Boolean value for the field.
+ */
+
+/**
+ * \fn void NoiseProtobufFormatter::addUInt32(NoiseProtobufTag_t tag, uint32_t value)
+ * \brief Adds an unsigned 32-bit integer field.
+ *
+ * \param tag Tag number for the field.
+ * \param value Unsigned 32-bit value for the field.
+ */
+
+/**
+ * \fn void NoiseProtobufFormatter::addUInt64(NoiseProtobufTag_t tag, uint64_t value)
+ * \brief Adds an unsigned 64-bit integer field.
+ *
+ * \param tag Tag number for the field.
+ * \param value Unsigned 64-bit value for the field.
+ */
+
+/**
+ * \fn void NoiseProtobufFormatter::addInt32(NoiseProtobufTag_t tag, int32_t value)
+ * \brief Adds a signed 32-bit integer field.
+ *
+ * \param tag Tag number for the field.
+ * \param value Signed 32-bit value for the field.
+ *
+ * This function uses the ZigZag encoding for the signed integer value.
+ */
+
+/**
+ * \fn void NoiseProtobufFormatter::addInt64(NoiseProtobufTag_t tag, int64_t value)
+ * \brief Adds a signed 64-bit integer field.
+ *
+ * \param tag Tag number for the field.
+ * \param value Signed 64-bit value for the field.
+ *
+ * This function uses the ZigZag encoding for the signed integer value.
+ */
+
+/**
+ * \brief Adds an arbitrary byte array as a field.
+ *
+ * \param tag Tag number for the field.
+ * \param data Points to the array of bytes for the field's value.
+ * \param len Number of bytes in the array.
+ */
+void NoiseProtobufFormatter::addBytes
+    (NoiseProtobufTag_t tag, const void *data, size_t len)
+{
+    if (!data && len > 0) {
+        err = true;
+        return;
+    }
+    addHeader(tag, 2);
+    if (sizeof(len) <= 4)
+        addVarUInt32(len);
+    else
+        addVarUInt64(len);
+    if (!err) {
+        if (len <= (maxsz - pos)) {
+            memcpy(buf + pos, data, len);
+            pos += len;
+        } else {
+            err = true;
+        }
+    }
+}
+
+/**
+ * \brief Adds a NUL-terminated string as a field.
+ *
+ * \param tag Tag number for the field.
+ * \param str String value for the field, NUL-terminated.
+ *
+ * If \a str is NULL, then an empty string will be added.
+ */
+void NoiseProtobufFormatter::addString(NoiseProtobufTag_t tag, const char *str)
+{
+    addBytes(tag, str, str ? strlen(str) : 0);
+}
+
+/**
+ * \fn void NoiseProtobufFormatter::addString(NoiseProtobufTag_t tag, const char *str, size_t len)
+ * \brief Adds a length-delimited string as a field.
+ *
+ * \param tag Tag number for the field.
+ * \param str String value for the field.
+ * \param len Number of bytes in the string value.
+ */
+
+#define ADD_BYTE(b) \
+    do { \
+        if (!err) { \
+            if (pos < maxsz) { \
+                buf[pos++] = (uint8_t)(b); \
+            } else { \
+                err = true; \
+            } \
+        } \
+    } while (0)
+
+/**
+ * \brief Starts an embedded message.
+ *
+ * \param tag Tag number for the embedded message.
+ *
+ * \return A reference to the start of the embedded message, to be passed
+ * to endEmbedded() when the application has finished adding nested fields.
+ *
+ * \note The size of the embedded data is limited to no more than 65535 bytes,
+ * to simplify the implementation of endEmbedded().  Since Noise messages are
+ * also limited to no more than 65535 bytes, this shouldn't be a problem
+ * in practice.
+ *
+ * \sa endEmbedded()
+ */
+size_t NoiseProtobufFormatter::startEmbedded(NoiseProtobufTag_t tag)
+{
+    addHeader(tag, 2);
+    size_t start = pos;
+    ADD_BYTE(0); // Placeholder to be filled in by endEmbedded().
+    return start;
+}
+
+/**
+ * \brief Ends an embedded message and returns to the previous level.
+ *
+ * \param start The value that was returned from startEmbedded() at the
+ * beginning of the embedded message.
+ *
+ * \sa startEmbedded()
+ */
+void NoiseProtobufFormatter::endEmbedded(size_t start)
+{
+    // If an error already occurred, then bail out.
+    if (err)
+        return;
+
+    // If the starting position is invalid, then bail out.
+    if (start >= pos) {
+        err = true;
+        return;
+    }
+
+    // Determine the actual length of the embedded message.
+    size_t len = pos - start - 1;
+
+    // Encode the length as 1, 2, or 3 bytes.  For the 2 and 3 byte
+    // versions we need to shift the message data up to make room.
+    if (len < (1U << 7)) {
+        buf[start] = (uint8_t)len;
+    } else if (len < (1U << 14)) {
+        if (pos < maxsz) {
+            memmove(buf + start + 2, buf + start + 1, len);
+            ++pos;
+            buf[start] = (uint8_t)(len | 0x80);
+            buf[start + 1] = (uint8_t)(len >> 7);
+        } else {
+            err = true;
+        }
+    } else if (len < (1U << 16)) {
+        if ((pos + 1) < maxsz) {
+            memmove(buf + start + 3, buf + start + 1, len);
+            pos += 2;
+            buf[start] = (uint8_t)(len | 0x80);
+            buf[start + 1] = (uint8_t)((len >> 7) | 0x80);
+            buf[start + 2] = (uint8_t)(len >> 14);
+        } else {
+            err = true;
+        }
+    } else {
+        err = true;
+    }
+}
+
+/**
+ * \fn void NoiseProtobufFormatter::addHeader(NoiseProtobufTag_t tag, uint8_t wireType)
+ * \brief Adds a protobuf tag header.
+ *
+ * \param tag Tag number for the field.
+ * \param wireType Protobuf wire type for the field; 0 for integer, 2 for
+ * length-delimited.
+ */
+
+/**
+ * \brief Adds an unsigned 14-bit value as a varint.
+ *
+ * \param value Unsigned 14-bit value to add.
+ */
+void NoiseProtobufFormatter::addVarUInt14(uint16_t value)
+{
+    if (value < (1U << 7)) {
+        ADD_BYTE(value);
+    } else {
+        ADD_BYTE(value | 0x80);
+        ADD_BYTE(value >> 7);
+    }
+}
+
+/**
+ * \brief Adds an unsigned 32-bit value as a varint.
+ *
+ * \param value Unsigned 32-bit value to add.
+ */
+void NoiseProtobufFormatter::addVarUInt32(uint32_t value)
+{
+    if (value < (1U << 7)) {
+        ADD_BYTE(value);
+    } else if (value < (1U << 14)) {
+        ADD_BYTE(value | 0x80);
+        ADD_BYTE(value >> 7);
+    } else if (value < (1U << 21)) {
+        ADD_BYTE(value | 0x80);
+        ADD_BYTE((value >> 7) | 0x80);
+        ADD_BYTE(value >> 14);
+    } else if (value < (1U << 28)) {
+        ADD_BYTE(value | 0x80);
+        ADD_BYTE((value >> 7) | 0x80);
+        ADD_BYTE((value >> 14) | 0x80);
+        ADD_BYTE(value >> 21);
+    } else {
+        ADD_BYTE(value | 0x80);
+        ADD_BYTE((value >> 7) | 0x80);
+        ADD_BYTE((value >> 14) | 0x80);
+        ADD_BYTE((value >> 21) | 0x80);
+        ADD_BYTE(value >> 28);
+    }
+}
+
+/**
+ * \brief Adds an unsigned 64-bit value as a varint.
+ *
+ * \param value Unsigned 64-bit value to add.
+ */
+void NoiseProtobufFormatter::addVarUInt64(uint64_t value)
+{
+    if (value < 0x100000000ULL) {
+        addVarUInt32((uint32_t)value);
+    } else {
+        while (value >= (1ULL << 7)) {
+            ADD_BYTE(value | 0x80);
+            value >>= 7;
+        }
+        ADD_BYTE(value);
+    }
+}
+
+/**
+ * \class NoiseProtobufParser NoiseProtobufs.h <NoiseProtobufs.h>
+ * \brief Parses data from a buffer using the protobufs format.
+ *
+ * This class provides support for parsing messages in the protobufs
+ * format.  Fields in a message consist of a tag followed by a value.
+ *
+ * This implementation provides a subset of the full protobufs encoding,
+ * limited to the types bool, uint32, uint64, sint32, sint64, string,
+ * bytes, and embedded messages.  In addition, tag numbers are limited
+ * to unsigned 8-bit values.
+ *
+ * Reference: https://developers.google.com/protocol-buffers/docs/encoding
+ *
+ * \sa NoiseProtobufFormatter
+ */
+
+/**
+ * \brief Constructs a new protobuf parser for reading the contents
+ * of a buffer.
+ *
+ * \param data Points to the buffer to parse.
+ * \param size Size of the buffer in bytes.
+ */
+NoiseProtobufParser::NoiseProtobufParser(const void *data, size_t size)
+    : buf((const uint8_t *)data)
+    , pos(0)
+    , end(size)
+    , ptr(0)
+    , value(0)
+    , wire(0xFF)
+    , err(false)
+{
+}
+
+/**
+ * \brief Destroys this protobuf parser.
+ */
+NoiseProtobufParser::~NoiseProtobufParser()
+{
+}
+
+/**
+ * \fn bool NoiseProtobufParser::error() const
+ * \brief Determine if an error occurred during parsing.
+ *
+ * \return Returns true if malformed data was found while parsing,
+ * false if parsing was successful.
+ */
+
+/**
+ * \brief Reads the next field from a protobuf-formatted message.
+ *
+ * \param tag Returns the tag number for the next field.
+ *
+ * \return Returns true if a new field was found, or false at the end
+ * of the message.  Also returns false if an error occurs.
+ */
+bool NoiseProtobufParser::readNext(NoiseProtobufTag_t &tag)
+{
+    tag = 0;
+    if (err || pos >= end)
+        return false;
+    uint64_t header = readVarint();
+    if (err)
+        return false;
+    if (header >= (256U << 3)) {
+        err = true;
+        return false;
+    }
+    tag = (NoiseProtobufTag_t)(header >> 3);
+    wire = (uint8_t)(header & 0x07);
+    if (wire == 0) {
+        value = readVarint();
+        return !err;
+    } else if (wire == 2) {
+        value = readVarint();
+        if (err)
+            return false;
+        if (value > (end - pos)) {
+            err = true;
+            return false;
+        }
+        ptr = pos;
+        pos += (size_t)value;
+        return true;
+    } else {
+        err = true;
+        return false;
+    }
+}
+
+/**
+ * \brief Reads a boolean value from the current field.
+ *
+ * \return The boolean value in the current field.
+ *
+ * This function will raise an error() if the current field is not boolean.
+ */
+bool NoiseProtobufParser::readBool()
+{
+    if (err)
+        return false;
+    if (wire != 0) {
+        err = true;
+        return false;
+    }
+    return value != 0;
+}
+
+/**
+ * \brief Reads an unsigned 32-bit integer value from the current field.
+ *
+ * \return The integer value in the current field.
+ *
+ * This function will raise an error() if the current field is not an
+ * integer or the value is out of range.
+ *
+ * \sa readUInt64(), readInt32()
+ */
+uint32_t NoiseProtobufParser::readUInt32()
+{
+    if (err)
+        return 0;
+    if (wire != 0 || value >= 0x100000000ULL) {
+        err = true;
+        return false;
+    }
+    return (uint32_t)value;
+}
+
+/**
+ * \brief Reads an unsigned 64-bit integer value from the current field.
+ *
+ * \return The integer value in the current field.
+ *
+ * This function will raise an error() if the current field is not an integer.
+ *
+ * \sa readUInt32(), readInt64()
+ */
+uint64_t NoiseProtobufParser::readUInt64()
+{
+    if (err)
+        return 0;
+    if (wire != 0) {
+        err = true;
+        return false;
+    }
+    return value;
+}
+
+/**
+ * \brief Reads a signed 32-bit integer value from the current field.
+ *
+ * \return The integer value in the current field.
+ *
+ * This function uses the ZigZag encoding for the signed integer value.
+ * An error() is raised if the current field is not an integer or the value
+ * is out of range.
+ *
+ * \sa readInt64(), readUInt32()
+ */
+int32_t NoiseProtobufParser::readInt32()
+{
+    if (err)
+        return 0;
+    if (wire != 0 || value >= 0x100000000ULL) {
+        err = true;
+        return false;
+    }
+    return ((int32_t)(value >> 1)) ^ (-((int32_t)(value & 0x01)));
+}
+
+/**
+ * \brief Reads a signed 64-bit integer value from the current field.
+ *
+ * \return The integer value in the current field.
+ *
+ * This function uses the ZigZag encoding for the signed integer value.
+ * An error() is raised if the current field is not an integer.
+ *
+ * \sa readInt32(), readUInt64()
+ */
+int64_t NoiseProtobufParser::readInt64()
+{
+    if (err)
+        return 0;
+    if (wire != 0) {
+        err = true;
+        return false;
+    }
+    return ((int64_t)(value >> 1)) ^ (-((int64_t)(value & 0x01)));
+}
+
+/**
+ * \brief Reads a string value from the current field.
+ *
+ * \param str Returns a pointer to the start of the string.  This points
+ * directly into the original buffer and will not be NUL-terminated.
+ *
+ * \return The length of the string in bytes.
+ *
+ * This function will raise an error() if the current field is not
+ * length-delimited.
+ *
+ * \sa readBytes()
+ */
+size_t NoiseProtobufParser::readString(const char * &str)
+{
+    if (err) {
+        str = 0;
+        return 0;
+    }
+    if (wire != 2) {
+        err = true;
+        str = 0;
+        return 0;
+    }
+    str = (const char *)(buf + ptr);
+    return (size_t)value;
+}
+
+/**
+ * \brief Reads a byte array from the current field.
+ *
+ * \param str Returns a pointer to the start of the byte array.
+ *
+ * \return The length of the byte array in bytes.
+ *
+ * This function will raise an error() if the current field is not
+ * length-delimited.
+ *
+ * \sa readString()
+ */
+size_t NoiseProtobufParser::readBytes(const void * &data)
+{
+    if (err) {
+        data = 0;
+        return 0;
+    }
+    if (wire != 2) {
+        err = true;
+        data = 0;
+        return 0;
+    }
+    data = (const void *)(buf + ptr);
+    return (size_t)value;
+}
+
+/**
+ * \brief Starts parsing an embedded message.
+ *
+ * \return A value to pass to endEmbedded() to pop out a level at the
+ * end of the embedded message.
+ *
+ * This function will raise an error() if the current field is not
+ * length-delimited.
+ *
+ * The following is an example of descending into an embedded message
+ * to parse all of the fields, and then returning to the previous
+ * message level at the end:
+ *
+ * \code
+ * size_t posn = parser.startEmbedded();
+ * while (parser.readNext(tag)) {
+ *     ...
+ * }
+ * parser.endEmbedded(posn);
+ * \endcode
+ *
+ * \sa endEmbedded()
+ */
+size_t NoiseProtobufParser::startEmbedded()
+{
+    if (err)
+        return 0;
+    if (wire != 2) {
+        err = true;
+        return 0;
+    }
+    size_t prev = end;
+    end = pos;
+    pos = ptr;
+    wire = 0xFF;
+    return prev;
+}
+
+/**
+ * \brief Ends parsing of an embedded message.
+ *
+ * \param posn The position in the outer message to return to.  This must be
+ * the return value from startEmbedded() for the same nesting level.
+ *
+ * \sa startEmbedded()
+ */
+void NoiseProtobufParser::endEmbedded(size_t posn)
+{
+    if (err)
+        return;
+    if (posn < end) {
+        err = true;
+        return;
+    }
+    pos = end;
+    end = posn;
+    wire = 0xFF;
+}
+
+/**
+ * \brief Reads a variable-length integer from the message.
+ *
+ * \return The integer value.
+ */
+uint64_t NoiseProtobufParser::readVarint()
+{
+    uint64_t value = 0;
+    unsigned bit = 0;
+    while (pos < end && (buf[pos] & 0x80) != 0) {
+        value |= ((uint64_t)(buf[pos] & 0x7F)) << bit;
+        bit += 7;
+        if (bit >= 63) {
+            err = true;
+            return 0;
+        }
+        ++pos;
+    }
+    if (pos >= end) {
+        err = true;
+        return 0;
+    }
+    if (bit >= 63 && (buf[pos] & 0xFE) != 0) {
+        err = true;
+        return 0;
+    }
+    value |= ((uint64_t)(buf[pos] & 0x7F)) << bit;
+    ++pos;
+    return value;
+}
diff --git a/libraries/NoiseProtocol/src/NoiseProtobufs.h b/libraries/NoiseProtocol/src/NoiseProtobufs.h
new file mode 100644
index 00000000..12e74f60
--- /dev/null
+++ b/libraries/NoiseProtocol/src/NoiseProtobufs.h
@@ -0,0 +1,205 @@
+/*
+ * Copyright (C) 2018 Southern Storm Software, Pty Ltd.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#ifndef NOISE_PROTOBUFS_h
+#define NOISE_PROTOBUFS_h
+
+#include <inttypes.h>
+#include <stddef.h>
+
+typedef uint8_t NoiseProtobufTag_t;
+
+namespace Noise
+{
+    // Tags for all NoiseLink negotiation options, for convenience.
+    // Not all of these are used for the NoiseTinyLink profile but we
+    // provide them in case we need more of full NoiseLink in the future.
+
+    /**
+     * \brief Protobuf tags for NoiseLink session negotiation requests
+     * from the client.
+     */
+    enum NegotiationRequest
+    {
+        ReqServerName       = 1,    /**< Server name */
+        ReqInitialProtocol  = 2,    /**< Initial Noise protocol to try */
+        ReqSwitchProtocol   = 3,    /**< List of supported fallback protocols */
+        ReqRetryProtocol    = 4,    /**< List of other non-fallback protocols */
+        ReqRejectedProtocol = 5,    /**< Previous protocol rejected by server */
+        ReqPSKId            = 6     /**< Identifier for the client's PSK */
+    };
+
+    /**
+     * \brief Protobuf tags for NoiseLink session negotiation responses
+     * from the server.
+     */
+    enum NegotiationResponse
+    {
+        RespSwitchProtocol  = 3,    /**< Switch to a fallback protocol */
+        RespRetryProtocol   = 4,    /**< Retry with a non-fallback protocol */
+        RespRejected        = 5     /**< Server totally rejected the client */
+    };
+
+    /**
+     * \brief Protobuf tags for NoiseLink options that may appear in
+     * handshake message payloads.
+     */
+    enum PayloadOptions
+    {
+        OptEvidenceReqType  = 1,    /**< Evidence request type */
+        OptEvidenceBlobType = 2,    /**< Evidence blob type */
+        OptEvidenceBlob     = 3,    /**< Evidence blob */
+        OptPSKId            = 4,    /**< Identifier for the client's PSK */
+        OptTransport        = 5     /**< Embedded transport options */
+    };
+
+    /**
+     * \brief Protobuf tags for NoiseLink transport options that may
+     * appear in handshake message payloads within an embedded message
+     * with the tag number OptTransport.
+     */
+    enum TransportOptions
+    {
+        TrMaxSendLength     = 1,    /**< Maximum send buffer length */
+        TrMaxRecvLength     = 2,    /**< Maximum receive buffer length */
+        TrContinuousRekey   = 3,    /**< Rekey after every message */
+        TrShortTerminated   = 4     /**< Terminate session on short message */
+    };
+};
+
+class NoiseProtobufFormatter
+{
+public:
+    NoiseProtobufFormatter(void *data, size_t maxSize);
+    ~NoiseProtobufFormatter();
+
+    size_t size() const { return pos; }
+    bool error() const { return err; }
+
+    void addBool(NoiseProtobufTag_t tag, bool value);
+
+    void addUInt32(NoiseProtobufTag_t tag, uint32_t value);
+    void addUInt64(NoiseProtobufTag_t tag, uint64_t value);
+    void addInt32(NoiseProtobufTag_t tag, int32_t value);
+    void addInt64(NoiseProtobufTag_t tag, int64_t value);
+
+    void addBytes(NoiseProtobufTag_t tag, const void *data, size_t len);
+
+    void addString(NoiseProtobufTag_t tag, const char *str);
+    void addString(NoiseProtobufTag_t tag, const char *str, size_t len);
+
+    size_t startEmbedded(NoiseProtobufTag_t tag);
+    void endEmbedded(size_t start);
+
+private:
+    uint8_t *buf;
+    size_t maxsz;
+    size_t pos;
+    bool err;
+
+    void addHeader(NoiseProtobufTag_t tag, uint8_t wireType);
+    void addVarUInt14(uint16_t value);
+    void addVarUInt32(uint32_t value);
+    void addVarUInt64(uint64_t value);
+};
+
+class NoiseProtobufParser
+{
+public:
+    NoiseProtobufParser(const void *data, size_t size);
+    ~NoiseProtobufParser();
+
+    bool error() const { return err; }
+
+    bool readNext(NoiseProtobufTag_t &tag);
+
+    bool readBool();
+    uint32_t readUInt32();
+    uint64_t readUInt64();
+    int32_t readInt32();
+    int64_t readInt64();
+
+    size_t readString(const char * &str);
+    size_t readBytes(const void * &data);
+
+    size_t startEmbedded();
+    void endEmbedded(size_t posn);
+
+private:
+    const uint8_t *buf;
+    size_t pos;
+    size_t end;
+    size_t ptr;
+    uint64_t value;
+    uint8_t wire;
+    bool err;
+
+    uint64_t readVarint();
+};
+
+inline void NoiseProtobufFormatter::addHeader
+    (NoiseProtobufTag_t tag, uint8_t wireType)
+{
+    addVarUInt14((((uint16_t)tag) << 3) | wireType);
+}
+
+inline void NoiseProtobufFormatter::addBool(NoiseProtobufTag_t tag, bool value)
+{
+    addHeader(tag, 0);
+    addVarUInt14(value ? 1 : 0);
+}
+
+inline void NoiseProtobufFormatter::addUInt32
+    (NoiseProtobufTag_t tag, uint32_t value)
+{
+    addHeader(tag, 0);
+    addVarUInt32(value);
+}
+
+inline void NoiseProtobufFormatter::addUInt64
+    (NoiseProtobufTag_t tag, uint64_t value)
+{
+    addHeader(tag, 0);
+    addVarUInt64(value);
+}
+
+inline void NoiseProtobufFormatter::addInt32
+    (NoiseProtobufTag_t tag, int32_t value)
+{
+    addHeader(tag, 0);
+    addVarUInt32((uint32_t)((value << 1) ^ (value >> 31)));
+}
+
+inline void NoiseProtobufFormatter::addInt64
+    (NoiseProtobufTag_t tag, int64_t value)
+{
+    addHeader(tag, 0);
+    addVarUInt64((uint64_t)((value << 1) ^ (value >> 63)));
+}
+
+inline void NoiseProtobufFormatter::addString
+    (NoiseProtobufTag_t tag, const char *str, size_t len)
+{
+    addBytes(tag, str, len);
+}
+
+#endif